ae Bat e Bi ttn ae ¥ gat th 4 i ay ie tat * by % FEE Sy ST AACS Wate RS Nal aes ee Foes ee 20 fn se = fe Si fae AAS, v ty * Ne Stray Ss a cS ay Stes sin? ee oe =, = = © Fone = ore = et aks Aah. we CORNELL UNIVERSITY. THE Roswell P. Flower Library THE GIFT OF ROSWELL P. FLOWER FOR THE USE OF THE N. Y. STATE VETERINARY COLLEGE 1897 8349-1 Cornell University Libra Dairy chemistry; a practical handbook for ATE DUE e GAYLORD Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001161763 DAIRY CHEMISTRY. NET BOOK..-This book is supplied to the Trade on terms which will not allow of Discount to the Public. CHARLES GRIFFIN & COMPANY, LTD. DAIRY CHEMISTRY. Charles Griffin & Company, Ltd., Publishers. Srconp Eprtion, Revised. In Crown $8vo. Pp. i-viii + 100. With Illustrations. 2s. 6d. net. DAIRY ANALYSIS (The Laboratory Book of). By H. DROOP RICHMOND, F.I.C. ConTENTS.—Introduction.—The Analysis of Milk Products——The Application of Analysis to the Solution of Problems.—The Analysis of Butter— Analysis of Cheese.— Tables for Calculation. APPENDIX.—INDEX. “ Without doubt the best contribution to the literature of its subject that has ever been written.”—Medical Times. ¥ Pp. i-xii + 259. With Photographs of Various Breeds of Cattle, &c. 6s. net. MILK: ITS PRODUCTION AND USES. With Chapters on Deiry Farming, The Diseases of Cattle, and on the Hyg ene and Control of Supplies. By EDWARD F. WILLOUGHBY, M.D., D.P.H. CoNTENTS.—Breeds, Caif Rearing, etc——Housing and Yards.—feed.—Diseases.— Legal Aspects of Diseases of Cattle-—Tuberculosis.—Inspection and Control.—Physi- ology of Milk, Chemical Composition.—Dietctics of Milk, Condensed Milk, Cream, etc., etc.—Therapeutics of Milk, Peptoniscd Milk, Koumiss, etc., etc.—Relations between Milk and Disease, Fevers, etc.—The Dairy.—Churning.—Ice.—Milk Analysis, Preservatives.— Control of Adulteration, Legal Aspects.—Bacteriological Examination.—Inoculation Experiments.—Cultures.—INDEX. “We cordially recommend it to everyone who has anything at all to do with milk.”— Dairy World. In Crown 8vo. Handsome Cloth. Pp. i-xi +1386. With 3 Plates aud 40 Illustrations in the Text. 4s. 6d. net. A MANUAL. OF : PRACTICAL AGRICULTURAL BACTERIOLOGY. By Paor. Dr. F. LOHNIS. Translated by W. STEVENSON, B.Sc., N.D.A., N.D.D., of the West of Scotland Agricul- tural college, and J. HUNTER SMITH, B.Sc. N.D.A., N.D.D., Assistant in the Laboratory of Dr. F. Lohnis, and Revised by the Author. CoNTENTS.—Introduction.—Books of Reference.—A. INTRODUCTION TO BACTERIO- LOGICAL TECHNIQUE, EXPERIMENTS WITH AIR, WATER, AND FOODSTUFFS.—Apparatus, Instruments, Laboratory Rules.—Culture Media.—Bacteria in Air.—Enumeration of Germs.—Forms of Colonies.—Bacteria in Water—lIsolating Bacteria.—Microscopic Examination.—Examination of Cultures.—Hay Bacteria.—Spores of Bacteria.—Describing and Identifying Bacteria.—Potato Bacteria—Anaerobic Methods.—Special Methods. B. Dalry BACTERIOLOGY.—Number of Bacteria in Milk —Sediment Test.—Reductase, Catalase, Boiling, and Alcohol Tests—Milk Fermentation and Curd Tests.—Detection of Foreign Infection—Bacterium Coli and Bacterium Aerogenes.—Aerobacter Group.— Lactic Acid Bacteria.—Rennet-Producing Bacteria.—Dissolving of Cascin. “We predict a wide demand for so excellent a guide.”—Journal of Economie Biology. Second Enition. In Large Crown 8vo. Cloth. Pp. i-ix + 250. ds. 6d. net. ELEMENTARY AGRICULTURAL CHEMISTRY. A Handbook for Junior Agricultural Students and Farmers. Br HERBERT INGLE, B.Sc, F.1LC., F.C.S., Fellow of the Royal Society of South Africa, of the Institute of Chemistry and of the Chemical Society. ConTENTS.—Introduction—The | Atmosphere-——The Soil.—Natural Waters.—The Plant.—Manures.—Crops.—The Animal Body.—Foods and Feeding of Animals.—The Dairy.—Miscellancous.—A PPENDIX.—INDEX. THE ABOVE WORK HAS BEEN ADOPTED BY THE EGYPTIAN GOVERNMENT. “ As an agricultural chemist Mr. Ingle excels.”—Farming World. “The teacher will have much cause to be grateful to Mr. Ingle.”—Nature. LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. DAIRY CHEMISTRY: A Practical BHandsook FOR DAIRY CHEMISTS AND OTHERS HAVING CONTROL OF DAIRIES. BY HENRY DROOP RICHMOND, FIC, ANALYST TO THE AYLESBURY DAIRY COMPANY, LIMITED. SECOND EDITION, REVISED. With Mumerous Tables and 49 Fllustrations, LONDON: CHARLES GRIFFIN & COMPANY, LIMITED; EXETER STREET, STRAND. 1914. [Al Rights Reserved.) Charles Griffin & Company, £td., Publishers. SEeconp Epr1ion, Revised. In Crown 8vo. Pp. i-viii + 100. With Illustrations. 2s. 6d. net. DAIRY ANALYSIS (The Laboratory Book of). By H. DROOP RICHMOND, F.I.C. CoNnTENTS.—Introduction.—The Analysis of Milk Products—The Application of Analysis to the Solution of Problems.—The Analysis of Butter—Analysis of Cheese.— Tables for Calculation.— APPENDIX.—INDEX. “ Without doubt the best contribution to the literature of its subject that has ever been written.”—Medical Times. - Pp. i-xii + 259. With Photographs of Various Breeds of Cattle, &c. 63s. net. MILK: ITS PRODUCTION AND USES. With Chapters on Dairy Farming, The Diseases of Cattle, and on the Hyg ene and Control of Supplies. By EDWARD F. WILLOUGHBY, M.D., D.P.H. ConTENTS.—Breeds, Caif Rearing, etc.—Housing and Yards.—ieed.—Diseases.— Legal Aspects of Diseases of Cattle—Tuberculosis.—Inspection and Control.—Physi- ology of Milk, Chemical Composition.—Dietctics of Milk, Condensed Milk, Cream, etc., etc.—Therapeutics of Milk, Peptoniscd Milk, Koumiss, etc., etc.—Relations between Milk and Disease, Fevers, etc.—The Dairy.—Churning.—Ice.—Milk Analysis, Preservatives.— Control of Adultcration, Legal Aspects.—Bacteriological Examination.—Inoculation Experiments.—Cultures.—INDEX. “We cordially recommend it to everyone who has anything at all to do with milk.”— Dairy World. In Crown 8vo. Handsome Cloth. Pp. i-xi +136. With 3 Plates aud 40 Illustrations in the Text. 4s. 6d. net. A MANUAL OF PRACTICAL AGRICULTURAL BACTERIOLOGY. By Pror. Dr. F. LOHNIS. Translated by W, STEVENSON, B.Sc., N.D.A., N.D.D., of the West of Scotland Agricul- tural college, aud J. HUNTER SMITH, B.Sc. N.D.A., N.D.D., Assistant in the Laboratory of Dr. ¥. Lohnis, and Revised by the Author. ContENTS.—Introduction.—Books of Reference.—A. INTRODUCTION TO BACTERIO- LOGICAL TECHNIQUE, EXPERIMENTS WITH AIR, WATER, AND FOODSTUFFS.—Apparatus, Instruments, Laboratory Rules.—Culture Media.—Bacteria in Air—Enumeration of Germs.—l’orms of Colonies.—Bacteria in Water.—Isolating Bacteria.—Microscopic Examination — Examination of Cultures.—Hay Bacteria.—Spores of Bacteria.— Describing and_ Identifying Bacteria.—Potato Bacteria—Anacrobic Methods.—Special Methods. B. DAIRY BACTERIOLOGY.—Number of Bacteria in Alilk —Sediment Test.—Reductase, Catalase, Boiling, and Alcohol Tests.—Milk Fermentation and Curd Tests.—Detection of Foreign Infection.—Bacterium Coli and Bacterium Aecrogenes.—Aerobacter Group.— Lactic Acid Bacteria.—Rennct-Producing Bacteria.—Dissolving of Casein. “We predict a wide demand for so excellent a guide.”—,Journal of Economic Biology. Sxconp Enition. In Large Crown Svo. Cloth. Pp. i-ix + 250. 4s. Gd. net, ELEMENTARY AGRICULTURAL CHEMISTRY. A Handbook for Junior Agricultural Students and Farmers. By HERBERT INGLE, B.Sc, F.LC., F.C.S., Fellow of the Royal Society of South Africa, of the Institute of Chemistry and of the Chemical Society. ConTENTS.—Introduction.—The Atmosphere.—The Soil.—Natural Waters.—The Plant.—Manures.—Crops.—The Animal Body.—Foods and Feeding of Animals.—The Dairy.—Misccllaneous.—A PPENDIX.—INDEX. THE ABOVE WORK HAS BEEN ADOPTED BY THE EGYPTIAN GOVERNMENT, “As an agricultural chemist Mr. Ingle excels.”—Farming World. “The teacher will have much cause to be grateful to Mr. Ingle.’—WNature. LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. DAIRY CHEMISTRY: A Practical HandBook FOR DAIRY CHEMISTS AND OTHERS HAVING CONTROL OF DAIRIES. BY HENRY DROOP RICHMOND, F.LC, ANALYST TO THE AYLESBURY DAIRY COMPANY, LIMITED. SECOND EDITION, REVISED. With Mumerous Tables and 49 Fllustrations, LONDON: CHARLES GRIFFIN & COMPANY, LIMITED; EXETER STREET, STRAND. 1914. {A Rights Reserved. } PREFACE TO SECOND EDITION. For more than seven years no copies of this book have heen obtainable, as owing to the author's ill-health it has been impossible to make the revision necessary to lying the work up to date. By lapse of time certain portions of the text had become obsolete, and these have been deleted and replaced by inatter based on the latest investigations. It has been found necessary to re-write many sections and to insert methods which have been devised since the book was first published, and this has involved the re-setting of the work throughout, although no alteration has been made in its plan or scope. New illustrations have been introduced and the index greatly improved, and it is hoped that public analysts and other chemists, medical officers, dairy farmers, and those interested in the chemistry of milk, butter, and cheese will tind the book of increased service. July, 1914. PREFACE. THE object of this work is to provide dairy chemists with a guide for the chemical control of dairy operations, the assumption being that a knowledge of dairying is already possessed; and public analysts, medical otticers, dairy farmers, and Students with a practically useful manual. The plan adopted is (1) to describe the chemical pro- perties of the constituents of milk; (2) to make use of these properties in the practical analysis of the various milks and milk products; and (3) to apply analytical methods to the control of dairy operations. In carrying out this work the author would especially notice that its value may be largely attributed to twa factors. The first is that Dr. Paul Vieth (now Professor in and Director of the Dairy Institute at Hameln) during his twelve years occupation as Analyst to the Aylesbury Dairy Company, accumulated a large number of obser- vations, which, as he remarked, contained very little theory, but a good deal of fact. This valuable material was handed over to me as_ hig successor, and has been made full use of in this work. The second factor is that the author owes much of his training as a dairy chemist to Mr. Otto Hehner, who enjoys so high a reputation in connection with butter analysis. It may also be stated that Mr. L. K. Boseley has kindly read the Section on the Analytical Characters of Sterilised Milk, that Mr. F. R. O'Shaughnessy has revised the mathe- matical portions of the book, and that Mr. A. W. Stokes bas supplied the information respecting those methods which bear his name. June, 1899, CONTENTS. Chapter I.—Introductory—The Constituents of Milk. PAGE General Composition, . 1 Chemical Properties of the Con- stituents of Milk, . 9 Milk-sugar, 9 Proteins, 18 Cascin, 28 Lactalbumin, 37 Mineral Constituents, 39 Fat, 41 Chapter II.—The Specific Gravity. : 58 Total Solids, 76 Ash, ‘ 81 Citric ‘Acid, Milk-sugar by Alcohol, Polarimetric, 90 by Reduction, 95 Cane Sugar, 101 Starch, 106 Chapter III.—Normal Milk : Products of Hydrolysis, Glycerol, Fatty Acids, Series C,,Hon41,COOH, Oleic, Linolic, Linolenic. Rancidity, Analysis of Milk. Fat, Gravimetric, Volumetric, Indirect, Proteins, from Total Nitrogen, Total Proteins, Casein and Albumin, Acidity, Aldehyde Figure, Lecithins, . Analysis of Milk Products, their Detection. Chemical Composition, 150 Limits and Variations, 150 Abnormal Milks, 153 Different Breeds, 154 Variations, 158 Colostrum, 161 Limits and Standards, 164 Influence of Feeding, 170 Adulteration and its Detection, 173 Preservatives, Detection, Preservation of Milk a a Action of Heat, Sterilised Milk, Condensed Milk. Milk Powders, Action of Cold, PAGE 47 47 50 54 55 56 57 106 123, 221 122 124 126 ru 133 136 137 137 its Adulterations and Alterations and Wi 183 189 191 193 198 201 203 CONTENTS. Chapter IV.—The Chemical Control of the Dairy. Duties of Dairy Chemist, Testing of Milk, Specific Gravity, Total Solids, F Fat, Leffmann-Beam Method, Gerber Method, . The Control of Milk during Delivery, Chapter V.—Biological and Sanitary Matters. Micro-organisms, Conveyance of Disease, Water Supply, Chemical Analysis, Bacteriological Examination, Composition, Variations, Theory of Churning, 5 Proximate Analysis, Water, : Solids not Fat and Salt, Preservatives, . . Analysis of Butter Fat, Volatile Fatty Acids, Saponification Equivalent, Baryta Value, Soluble and Insoluble Fatty Acids, . Phytosteryl Acetate Test, Specific Colour Tests, Action of Rennet, ‘Curd and Whey, Rennet, ‘ Testing, Cheese, Classification, Composition, Proteins, Ripening, . Analysis, PAGE PAGE 207 | Solution of si il icc! 244 213 | Skim Milk, 253 213 | Cream, . 264 219; Thickness, . : 270 221| Artificial Thickening, 273 228 | Homogenised Milk, : 274 242 275 | Sanitary Precautions, 295 282} Koumiss, 297 284 | Kephir, 299 284. Mazoum, 300 291] Bulgarian Sour Milk, 300 Chapter VI.—Butier. 301 | Behaviour with Solvents, 331 302 | Iodine and Bromine Absorption, 333 305 | Heat evolved by Sulphuric Acid, 336 308 | Physical Examination, 338 309] Microscopical Examination, | 338 310| Density, ‘ : 342 311 Refractive Index, 345 314] Viscosity, . 351 316] Behaviour on Melting, 352 324] Detection of Adulteration, 353 325 | Influence of Keeping, 354 Detection of Rancidity, . 357 326 | Buttermilk, ~ BbT 329 | Chemical Control of Chumning, , 359 330 | Use of Starters, . 861 Chapter VII.—Other Milk Products. 362 | Control of Cheese- -Making, 384 362 | Commercial Milk-sugar, 385 364] Analysis, 385 365| Adulteration, 386 365 | Junkets, 387 366 | Casein Preparations, 387 369) Analysis, 388 372 | Milk Wine, 389 373 | Milk Cocoa, . 389 383 | Milk Chocolate, _Adulteration, 389 CONTENTS. xi Chapter VIII—The Milk a ana other than the Cow. PAGE Classification, F "390 | The Milk of the Ass, . 404 Human Milk, 392 | Milk as a Food and a Medicine, 405 Analysis, . 395 | Milk as a Food for Infants, . 407 The Milk of the Buffalo, 397 | Peptonised Milk, 408 The Milk of the Ewe, 402 | Diabetic Milk, . 408 The Milk of the Goat, . 403 | Koumiss, . 409 The Milk of the Mare, . 403 Chapter IX.—Standardisation and Calibration of Apparatus. Weights, 410| Leffmann-Beam or Gerber Burettes, 412 Bottles, . . 413 Pipettes, 413 | Lactometers, 414 Flasks, . F 413 | Thermometers, 414 AppeENDIXx, Useful Tables, 415 INDEX, F , 425 DALI «CAM Te Ts CHAPTER TIT. INTRODUCTORY—THUE CONSTITUENTS OF MILK, Contents—General Composition—Fat—Sugar—Proteins—Salts—Colour —Reaction—Milk-Sugar—Glucose—Products derived from Milk- Sugar—The Proteins of Milk—Products of Hydrolysis—General Action of Hydrolysis—Mineral Constituents— Other Constituents of Milk—The Gases of Milk—The Fat of Milk—Products of Hydrolysis —Fatty Acids—Other Compounds—Rancidity. General Composition.—Milk is the normal secretion of the mammary glands of a mammal; the milk of all mammals has a similar composition, consisting of fat, sugar, protein, mineral constituents, and small quantities of other compounds. The milk of the cow has been studied in greater detail than that of any other animal on account of the extended use of this animal’s milk and the products derived from it as human food; the greater portion of this work will, therefore, be devoted to the consideration of the chemical properties of cow’s milk, and the expressions ‘“‘ milk,” “‘ butter,” etc., must be taken as applying to the products derived from the cow, unless described to the contrary. Much, however, that is stated with regard to the cow may be taken as applying equally to the milk of other animals; but our knowledge of the chemical composition of the milk of any animal, except the cow, is very incomplete. Studies, more or less incomplete, have been made of the milk yielded by woman, the goat, the ass, the mare, the gamoose, and the sheep, and analyses, few in number, have been made of the milk of other mammals, both terrestrial and marine. It is probable that there exist wider differences than are vet recognised between the milk vielded bv different animals. Fat.—The fat in milk is of peculiar and complex composition ; it differs from ali other fats in that it contains compound gly- cerides partly built up of fatty acids of low nee ee 2 INTRODUCTORY—THE CONSTITUENTS OF MILK. It exists in milk in the form of small globules. Many have thought that a true membrane surrounds each globule, and Béchamp considers this view as proved by the behaviour of milk when treated with ether. He finds that milk is capable of dissolving a very large quantity of ether, much more than would be dissolved in the aqueous portion of the milk, and he explains this by the theory that the ether is dissolved by the fat con- tained in the membranes. His theory assumes that the ether has passed into the membrane by the process known as “ endos- mose,” and that the endosmose is stopped only when the pressure exerted by the distended membrane is equal to the osmotic pressure ; the presence of fat to small amount in the excess of ether which separates is explained as partly due to a process of exosmose of the fat within the membrane concurrently with Fig. 1.—Fat Globules in Milk. the endosmose, and partly to the bursting of a number of the globules. The opponents of his theory urge that the amount of fat in the excess of ether which separates, if this be great, is too large to be explained by assuming exosmose, or the bursting of the globules, which should not take place to a greater degree with a large excess of ether than with a small. : Storch has put forward the view that no real membrane exists round the fat globules, but that a gelatinous “mucoid”? mem- brane (slim-membran, in Danish) surrounds them; this consists according to him, of a combination of 6 parts of a ‘‘ mucoid ” protein with 94 parts of water (membran-slim). He bases his view— (1) On the fact of the existence of this mucoid substance in FAT. 3 cream and butter, and therefore presumably in milk; he proves its existence, and, in fact, isolates it, by washing cream with water and separating the layer of globules till milk-sugar, casein, etc., are all removed. (2) On the behaviour of milk with ether; his experience differs from that of Béchamp, as, while the latter finds that ether expands the globules to several times their normal size, Storch states that they are not swollen. (3) On the appearance of the fat globules under the micro- scope when the milk has been stained by ammoniacal picro- carmine, and the layer of cream treated with successive quan- tities of water till all the milk-sugar has been removed; he notices that a stained layer is present round each fat globule. There is much to be said in favour of Storch’s reasoning, and other evidence may be adduced in favour of it. Butter, in which the globules are certainly more naked than in milk, can be prepared with about 85 to 86 per cent. of fat; this is solid, hecause the solid fat globules are in close proximity : cream, on the other hand, cannot be prepared with more than about 72 per cent. of fat, and as this has the same consistency as butter at the sume temperature, it may be assumed that the globules are in equally close proximity. This would agree with the view that each vlobule was surrounded by a layer, which increased the effective size. Storch himself has, however, shown that the fat in butter does not exist in the form of globules, but as a nearly homogeneous mass, containing water globules. Storch has ad- duced evidence, based on the property of ether to emulsify this mucoid substance, that butter-milk contains a larger amount than milk, and on this has based a theory that churning consists of rubbing off the membrane, with the effect that the globules coalesce. The author has experimentally proved the fact that buttermilk is richer in mucoid substance than milk by separating it with a cream separator. Storch considers this as confirmatory evidence of the presence of a membrane. The evidence is, however, inadequate to settle the question, and in some respects may be held to show that a membrane does not exist. As the author has succeeded in isolating the protein, he has no doubt of its existence: by estimating in butter and buttermilk the water, fat, milk-sugar, protei, and ash, Storch finds that there is much less milk-sugar and more protein in proportion to the water in butter than in buttermilk; he cal- culates the proportion of protein and water equivalent to the milk-sugar in butter on the supposition that the milk-sugar is an index of the buttermilk left in the butter, and finds a residue of the following percentage composition in three series of ex- periments :— 4 INTRODUCTORY-—-THE CONSTITUENTS OF MILK. | i II ll 1 Water, ‘i ‘ 93-15 90°37 92-55 Protein, ‘ 5-67 8-27 6-42 Ash, A 118 1-36 1-03 | The results from the three experiments agree very well, con- sidering the smallness of the actual quantities. From the results of experiments, in which cream was treated with a 33 pet cent. solution of cane-sugar (used to promote the separation of the layer of fat globules), and the fatty layer separated, and the procedure repeated several times, Storch deduces the proportion of mucoid substance to fat as 38°4 to 100. From these experiments it is evident that cream containing 50 per cent. of fat should contain 19 per cent. of mucoid sub- stance, and only 31 per cent. of the other constituents of milk ; in other words, cream containing 50 per cent. of fat should, if Storch’s hypothesis be true, only contain ;°,), of the milk-sugar in the skim milk. Analysis, however, shows that it actually contains 735. If a membrane be present, the ratio of solids not fat to water in cream should differ from the ratio found in milk (except in the case that the ratio of solids to water in the membrane is the same as that in milk); the author has shown, and is confirmed by Smith and Leonard, that the ratio remains the same. The experiments of Storch and Béchamp on the mixing of ether with milk are capable of an explanation quite different from that which they attach to it when the laws governing the distribution of a substance between two immiscible solvents are taken into account. We may regard milk as a mixture of an aqueous solution with a large number of fat globules; on gently shaking up with ether it is evident that very few, if any, of the fat globules come into contact with the ether, but only with an aqueous solution of ether. According to the law, the ether should distribute itself between the fat and the aqueous solution in proportion to the solubility in each; if the fat is liquid we should expect a large proportion of the ether to pass into the globules, and they would naturally swell; if, on the other hand, the fat is solid we would not expect it to take up any appreciable proportion of ether, and the globules would remain the same size. In neither case would any appreciable amount of fat pass into the excess of ether which separates, as fat is very little soluble in an aqueous solution of ether. : Béchamp used milk which had not been strongly cooled, but FAT. 5 which was freshly drawn, and cooled simply by radiation. Under these conditions the author has obtained evidence that the fat globules are liquid. Storch gives no indication as to the con- dition of the milk used by him, but it is the common practice in Denmark to cool all milk to a very low temperature with ice immediately after milking. These conditions, according to the author’s experience, facilitate the solidification of the fat. It is not improbable that the apparent discrepancy between Béchamp and Storch is due to a difference of conditions. In concluding that the staining of a layer round the fat globules proved the presence of a solid membrane, Storch appears to have overlooked the surface energy of small particles, which would cause a layer composed wholly of liquid to be formed round cach globule. The appearance noticed by Storch is quite explic- able without the assumption that a membrane exists, and, indeed, is somewhat at variance with this view. If there were au solid or mucoid layer it should have a sharply defined outer edge. According to Storch’s description this is wanting; the staining is deepest nearest to the globule, and fades imperceptibly away, an appearance quite compatible with the view that a condensed liquid laver is present. Though data do not exist for calculating the force with which a semi-solid laver would be held by surface energy, it appears reasonable to suppose that it would be impossible to remove this by churning—i.c., friction between globules—therefore butter could not be made were Storch’s hypothesis correct. By homogenising cream—?.e., breaking up the fat into very minute globules—it is found that it is impossible to churn the fat into butter; this operation woald certainly remove a mem- brane, and according to Storch’s theory should facilitate churning. If Ntorch’s view were correct, it would he expected that the membrane would bear such a proportion to the smallest fat vlobules that their density would be equal to that of the milk serum, and the last traces of fat could not be removed by centri- fugal force. By means of an efficient separator it is possible, on running milk twice, to obtain samples of separated milk in which the percentage of fat is so small that it does not reach the second place of decimals per cent.: this fact, while not definitely disproving Storch’s view, is further evidence against it. The following facts seem to definitely disprove Storch’s view :— (1) The ratio of the milk-sugar and protein in cream is the same as in the separated milk. (2) When milk or cream is stained no layer can be detected round the globules until the aqueous portion is washed away. There are, however, many stained particles (probably mucoid protein) quite independent of the fat globules. 6 INTRODUCTORY—THE CONSTITUENTS OF MILK. (3) The mucoid protein can only be separated with the fat globules if the density of the serum is increased (by the addition of cane sugar) till it is greater than the density of mucoid protein (10228) ; this proves that it is independent of the fat globules. }:4 Milk is regarded by others as an emulsion, and they see no reason why an emulsion of fat containing ether should not exist. of the same nature as that of fat alone; these regard the fact that while a small quantity of ether does not extract the fat to any extent from milk, a large quantity does so with a much nearer approach to completeness, to favour the idea that a membrane does not exist round the globules. If milk is precipitated with a solution of nitrate of mercury, which coagulates all the protem of milk, the whole of the fat is removed from suspension, even if it exceeds the protein in weight many times. That this is. not due to the precipitation of substances distributed through- out the solution, and the enclosing of the fat therein, is shown by the fact that when the casein, which is equally distributed throughout the solution, is precipitated by means of rennet. a considerable proportion of the fat is not enclosed. This fact can hardly be used as an argument that a membrane exists, as the two modes of precipitation differ essentially ; the mercury precipitate commences to settle immediately, leaving the solution clear, while rennet gradually reduces the milk to a semi-solid mass, which does not yield a precipitate until the whole has. received considerable agitation. As a strong argument against the existence of a membrane may be cited the possibility of preparing artificial emulsions of fats in a finely divided state with milk from which the natural fat has been removed; these emulsions partake very largely of the character of milk. Emul- sions of a similar nature can be prepared with other substances, and their behaviour in a great number of respects resembles that of milk. The gene al consensus of opinion among chemists: who may be regarded as authorities on this point is that the fat in milk is not surrounded by a membrane, and, therefore, that it is a true emulsion, There is very little doubt that a layer exists round each fat globule; this is probably formed by an attraction due to surface energy, a force akin to that which causes the phenomenon known as capillary attraction. Much of the evidence which has been taken as proof of the existence of a membrane round the globules is only evidence of the presence of a layer of some sort, but not necessarily membranous. Bauer concludes from surface tension experiments that a solid layer exists round the fat globules, and that this probably contains some fat. . The author and 8. O. Richmond have obtained evidence that the fat globules in milk solidify when cooled below their melting FAT—SUGAR—PROTEINS. 7 point; the solidification is, however, a process which takes a considerable amount of time (some hours), and it appears pro- bable that an apparent reversal of the laws of nature takes place. When a substance cools heat is given out or energy is evolved. When a very small globule cools it contracts, and the surface energy is increased—that is to say, energy is absorbed. As this energy can only be supplied as heat abstracted from the aqueous portion of the milk, it follows that, as the fat globules and aqueous portion are at approximately the same temperature. the passage of energy from one to the other will be slow, and, therefore, that solidification of the globules will be but a slow process. Burri and Nussbaumer find that the surface tension of milk is diminished by cooling, and Bauer attributes this to the solidifica- tion of the fat, as the original value can be very nearly restored by heating above the melting point of fat. Sugar.—The sugar in milk is of a peculiar nature; that of cow’s milk is called “lactose,” or, more commonly, sugar of milk. It is generally assumed that all milks contain the same sugar, but of this there is some doubt. The author, in conjunction with Pappel, has identified in the milk of the ‘‘ gamoose,” or Egyptian buffalo, a sugar distinct from lactose, to which the name of ‘ tewfikose” has been given. The sugar of the milk of the mare has the property of easily undergoing alcoholic fer- mentation, a property not possessed by lactose. According to the experiments of Carter and the author, the sugar of human milk is not identical with that of the milk of the cow. The sweetness of milk is entirely due to the sugar contained in it; the sugar of milk is many times less sweet than cane sugar. It is very easy of digestion, even by young children. Proteins.—It is in the proteins that the milk of different animals show the most marked variations. They may be divided broadly into two classes—those which give a curd on the addition of an acid, and those which do not. In the first class are included the milk yielded by the cow, the goat, the gamoose, ete. ; and in the second human milk, that of the mare, and that of the ass may be cited as examples. In the first class the curd is composed of casein, which is combined with phosphates of the alkaline earths: while in the second this is replaced by a similar protein, which is not, however, combined with phosphates. It is possible that the difference between the proteins of the two classes is simply dependent on the presence or absence of the phosphates, but the chemistry of these bodies is not yet sufficiently advanced to decide this. Besides casein, or a similar body, there exists in all milks a second protein called albumin; this differs from casein by not being precipitated by acids, and by being coagulated 8 INTRODUCTORY—THE CONSTITUENTS OF MILK. by heat. Other proteins have been described in milk, but many of them are only decomposition products of casein or albumin, which were formed during the process adopted for the removal of the other proteins. Evidence has been adduced of a third protein in milk; Storch’s mucoid protein has already been referred to. Béchamp has described a starch-liquefying enzyme, and lately Babcock and Russell have separated a proteolytic enzyme. There also exists an enzyme which has the properties of a peroxydase, which may be identical with those of Béchamp and Babcock and Russell. The casein in milk is not in a state of true solution; it is probably in the state described by Picton and Linder as “ pseudo- solution.” They have shown that this state is due to the exist- ence of particles in the solution not sufficiently large to settle under the influence of gravity, but which will interfere with the passage of light; they can also be separated by a current of electricity, or by passage of the solution through a porous jar. They show also that there is no sharp dividing line between crystalloids and colloids in solution, substances in pseudo-solu- tion, and substances in suspension. In milk we have the four states represented—the fat is in suspension, the casein in pseudo- solution, the albumin in solution as a colloid, and the milk- sugar in solution as a crystalloid; these four states are probably due to the size of the conglomerates of molecules or particles. Salts.—The salts of milk are not yet fully studied ; the presence of chlorides, phosphates, and sulphates of sodium, potassium, calcium, and magnesium is generally admitted. Salts of organic acids are also present; Henkel has described citric acid, and Béchamp acetic acid, but this latter result is not universally accepted. Béchamp also maintains that the casein and albumin exist in milk as salts of alkalies; there is much to recommend this view. A solution greatly resembling milk can be prepared in which casein undoubtedly exists combined with an alkali, while it has not been found possible to dissolve casein to an appreciable extent unless an alkali is present: milk does not taste sour until an appreciable acidity has developed ; at about the same point it curdles on heating ; it is proved that this is due to the acid developed displacing the alkali from its compound with casein. It is also found impossible to coagulate the albumin in milk unless a certain amount of free acid is added, and this fact accords well with the theory of Béchamp. Sdldner has also adduced evidence in proof of this view, Besides the constituents enumerated above, milk contains traces of other compounds; among these may be mentioned urea and other bases, an odoriferous principle, and a colouring- MILK-SUGAR. 9 matter; these two latter occur in very small amount, and are of unknown composition. Colour.—The colour of milk is nearly white, due not to the presence of the colouring-matter just mentioned, which accu- mulates in the fat, but to the interference with the passage of light by the casein in pseudo-solution. When milk is viewed in thin layers, especially if the bulk of the fat has been removed, it has a bluish tint: the bluish tint can hardly be called a colour ; it partakes more of the nature of a fluorescence, and the trans- mitted light is polarised to a slight degree. The fat globules, being very much lighter than the medium in which they are suspended and being of sufficient mass to over- come the viscosity of the fluid, have a tendency to rise and form a layer of cream on the surface of the milk when left to rest. Reaction.— Milk has always, when fresh, an amphoteric re- action—7.c., it turns blue litmus paper slightly red and red litmus slightly blue. A similar reaction is possessed by certain phos- phate solutions, and it is to the presence of such in milk that this reaction is duc, The true explanation is that the acidity of milk is due to mono- and di-acid phosphates, and the strength of these acid salts is of the same order as the strength of the acid of litmus. When blue litmus is used for testing, a substance more alkaline than the milk is introduced and equilibrium is set up; alkali passes from the litmus to the milk, and conse- quently the blue litmus is reddened. When red litmus is used an acid substance is introduced, and for the attainment of equilibrium alkali must pass from the milk to the litmus, thereby turning it slehtly blue. This reaction has acquired a false importance, owing to the erroneous idea that neutrality as measured by the action of litmus is chemical neutrality ; with the recognition of the fallacy of this idea the importance of the amphoteric reaction vanishes. Tue CHEMICAL PROPERTIES OF THE CONSTITUENTS OF MILE. Milk-Sugar, Lactose (Lacton or Lacto-biose), CysH»s.0,, OH). —Properties.—This sugar is found in the milk of the cow and probably in that of most other mammals. It is a hexa-biose, and belongs to the class of aldehydes (aldoses), or rather alde- hydrols. It has the constitution of a galactose-glucoside, and on hydrolysis by acids vields a mixture of galactose and glucose. Fischer assigns the following constitution to it :— OCH; CH,OH. 4(CHOH)CH OCH3(CHOH)COH. 10 INTRODUCTORY—THE CONSTITUENTS OF MILK. The aldehyde group of the galactose has been eliminated in milk-sugar, while that of the glucose remains. This is shown by the reactions of several derivatives of milk-sugar; by heating milk-sugar with phenylhydrazine and acetic acid, phenyl-lactos- azone is formed, which yields an osone on treatment with strong hydrochloric acid ; this, by boiling with hydrochloric acid, yields a mixture of galactose and glucosone. By treatment again with phenylhydrazine, the glucosone forms phenylglucosazone almost immediately, and, on warming, phenylgalactosazone is precipi- tated. A clear demonstration is thus afforded that the aldehyde group of the glucose only remains. By oxidation with bromine, lactobionic acid is formed, which is hydrolysed by acids to gluconic acid and galactose; again showing that the galactose group is modified. The reactions of milk-sugar, which are all displayed in solu- tion, are those of an aldehyde, but from its formation of stable hydrated compounds it appears more correct to regard it as an aldehydrol. Modifications.—Milk-sugar exists in several modifications which are distinguished from each other chiefly by then beha- viour towards polarised light. The best known modification is the hydrated c-milk-sugar, usually known as crystallised milk-sugar; this is the form in which it crystallises from water. The «-modification exhibits multi-rotation—z.e., when dissolved in water it has a much higher specific rotation than that which it attains after a lapse of time. The author has found that when more milk-sugar than will immediately dissolve is shaken with water it causes a lowering of the temperature of the solution by about 055°C. By shaking up the finely powdered sugar with water, a solution is obtained containing about 7°5 grammes per 100 c.c. at 15° C., the quantity dissolved increasing roughly about 071 gramme per 100 c.c. for each degree above 15° C. No thermal change was detected in this solution by a thermometer reading to 0°01° C., but the temperature rose steadily till it attained that of the surrounding atmosphere, which was kept constant; the rate of rise was identical with that of a previously prepared solution of milk- sugar of the same strength, which had been cooled to the same temperature. Brown and Pickering have, however, shown that a slight thermal change takes place with change of rotatory power (++ 0°19 calorie per gramme). No change in density or molecular weight indicated by freezing point determination was observed on keeping solutions of milk-sugar, though the specific rotation varied very widely. It is usually stated that a freshly prepared solution of «milk sugar contains 14°55 per cent. at 10° C.; while by long standing MODIFICATIONS OF MILK-SUGAR. 11 in contact with milk-sugar, or by boiling, a saturated solution containing 21°64 per cent. can be obtained. The author is unable to confirm the figure for the freshly prepared solution. The density of well formed crystals is 1545 at 3 bad. crystals—i.e., those which are strained, have, however, a lower density. The hydrated u-modification is practically insoluble in alcohol, ether (in ether saturated with water it dissolves to the extent of 000075 gramme per 100 c.c.), chloroform, benzene, and other organic solvents. It is slightly, but distinctly, soluble in amyl alcohol on boiling, but is probably dehydrated. It is unaffected by heating to 100° C., but the water of hydra- tion is given off at 130° C.; at 170° a change takes place with formation of lacto-caramel, and it melts at 213°5° C. When dissolved in water the specific rotatory power remains constant for a short period, 3 minutes at 20° C., 6 minutes at 15° C., and 15 minutes at 10° C.; the rotation then gradually falls. The following series of observations (Table I.) will show the nature of the change in rotation :— TABLE I.—Cuance or Roration or «-MILK-SUGAR IN SOLUTION, Time 'T. Observed Rotation, Ra, Calettlated Rotation | Difference. _ sa, oe eee me 22 min L273? ; + 0:02 DAT ys TAGS? | ‘ — 0°03 32° 5 12-68" Sia | + 0°07 ee 12°83° ce! 0-08 Sey wis | + 0-02 GO yy 12°73° + 0°02 TE ss 12-48? ‘ 1245 + 0°01 O25 ay pee? ees a O30 55 11°83” l 11-91° + 0°08 BO 4, 11-58? 115° = 1 1 ABR, : Lieear Lista? =, OF 12 NAS 10-73" LO" 2" 0-01 i 360-0. ,, 8-03? ; S03? on 24 hrs. 79S = Re ; TS! The solution used was examined in a 198-4 mm. tube using the sodium light ; two determinations gave 7°090 and 7-072 per cent. of anhydrous milk-sugar, and, as the solution had a density of 1°0265 at 17° (the temperature of observation), it contained 7651 grammes of hydrated milk-sugar per 100 c.c. 12 INTRODUCTORY—THE UONSTITUENTS OF MILK. It is seen that the rotation is approximately constant for the first 6 minutes, and averages 12°75°, which corresponds to [«]p = 83°99°. After 24 hours the rotation is constant at 7°95°, which corresponds to [¢]> = 52°37°. The figures given in the “ calculated ” column are deduced by the formula— logy (R, — R) = 0:68124 — 0-00491 (T — 6). The fact that the fall in rotation is expressed by a logarithmic curve shows that the rate of change is proportional to the amount of unchanged substance in solution; this is Harcourt’s law of mono-molecular change. The ratio between the initial rotation and the final rotation, which may be called the bi-rotation ratio, is ees = = 1604. The mean of several determinations has led to the value for {@]p of the hydrated ¢-modification = 84°0°, and the bi-rotation ratio 1°6; these are the figures given by Schmoeger, who, how- ever, assigned to them an approximate value only. The small amount of thermal change during change of rotation and absence of change in density and freezing point show, with a considerable degree of probability, that the change manifested by alteration in rotation is intra-molecular. It is probably caused by the migration of the water of hydration from one carbon atom to another. The anhydrous modification of the #-modification is obtained by heating the hydrated modification to 130° C. It is hygro- scopic and dissolves in water with evolution of heat; the solu- bility is much greater than that of the hydrated modification. The optical properties are stated by Schmoeger to be the same as those of the hydrated modification. Both the «- and 8-modifications are converted on dissolving in water into a stable equilibrium form. Schmoeger gives the specific rotatory power [¢]p as 52°53° at 20° C., diminishing 0°075° for each degree C. above and this increasing for lower temperatures. The author can absolutely confirm these numbers. It has never been prepared pure in the solid state, though con- siderable evidence of its existence, both in the hydrated and anhydrous modifications, has been obtained by the author, By the addition of alcohol or, better, ether to a very highly supersaturated hot solution of milk-sugar, it sets to a solid mass, which may be dried in vacuo, and does not then lose weight at 100° C., but which contains, however, a certain amount—2 to 4 per cent.—of water of hydration which is lost at 130° C. There is no appreciable change in rotation on dissolving this product MODIFICATIONS OF MILK-SUGAR. 13 in water and taking readings at intervals; as some of the read- ings obtained have been above, and some below, that ultimately obtained, it is probable ‘that the very slight differences noticed were due to errors of observation. By precipitating less strong solutions of milk-sugar by alcohol, products can be obtained which contain very nearly, if not quite, the same percentage of water as the hydrated «modification. but which have a much smaller, but not constant, bi-rotation ratio. These also give a constant rotation for a few minutes on dissolving in water and behave as mixtures of the « and #-modi- fications. They have a less density than the «modification, but it is not certain whether this may not be due to the very imperfect crystallisation which takes place, the products appearing nearly amorphous. By evaporating aqueous solutions of milk-sugar on the water bath, an anhydrous sugar can be obtained, which has a very slight bi-rotation ratio, which is not constant. As this varies from 1°09 to 1°02, such sugar probably consists of the equilibrium form, mixed with a small amount of the «modification. A specimen having a bi-rotation ratio of 1°03 had a density of 1585 at ae 5 2, and dissolved in water with a slight evolution of heat. There is some evidence that the hydrated 8-modification dis- solves in water with a greater absorption of heat than the «-modi- fication, as the mixtures obtained by precipitation with alcohol cause a greater lowering of temperature than the «modification. The solubility appears to be greater. There exists also a §-modification, which is obtained in the anhydrous form by the rapid evaporation of aqueous solutions in metallic vessels. It has a specific rotatory power of 32°7° at the moment of solution. Schmoeger states that it has a bi-rotation ratio of i which Tanret confirms. The rate of change of the «- and 6-modifications is the same for the same temperature. By the addition of ammonia, the change which the ¢- and 3- modifications slowly undergo on solution in water becomes almost instantaneous. By raismg the temperature, the rate of change is increased and is practically instantaneous on boiling. The solubility of milk-sugar in water is small compared with the solubilities of other carbohvdrates ; owing to the tendency of milk-sugar to form supersaturated solutions it is difficult to determine its exact solubility, but the mother liquors from which crystals have deposited usually contain about 21 per cent. The «-modification crystallises in wedge-shaped forms which 14 INTRODUCTORY—THE CONSTITUENTS OF MILK. often have the face at the end of the wedge greatly prolonged. The f-modification crystallises in needles. The taste of the «-modification is not sweet, and from its comparative insolubility it appears to be gritty. In solution milk-sugar has a sweet taste of about a quarter the sweetness of cane-sugar. As already stated, on heating to 170° C. it turns brown, and lacto-caramel is formed ; a similar change takes place by heating an aqueous solution to 100° C. for some hours; the presence of small amounts of alkali greatly increase the browning of the solution. The rotatory power is greatly diminished. Chemical Properties.—Milk-sugar, in common with other aldoses and ketoses, reduces alkaline solutions of copper, silver, and mercury, forming cuprous oxide, and metallic silver and mercury respectively. On this fact the well-known Febling’s test for sugar is based. The amount of reduction is constant for fixed amounts of milk-sugar under the same conditions, and is nearly proportional to the amount of milk-sugar. Each sugar shows a definite amount of reduction in the same way,-and a valuable method for distinguishing them is thus available. The difference between reduction by various sugars is not due to any difference in the reaction with the metallic salt, but depends on their relative stability towards alkalies. On warming with dilute nitric acid (sp. gr. 1:2) an energetic action takes place, mucic acid, together with saccharic, oxalic, and other acids being formed; the mucic acid, which can be separated by its relative insolubility, amounts to about 32 per cent. of the weight of the milk-sugar. This is due to the galactose portion of the milk-sugar. Strong nitric acid (sp. gr. 15) mixed with sulphuric acid, to absorb the water formed in the reaction, gives rise to the formation of tri- and penta-nitrates; both these compounds have explosive properties. The penta-nitrate is a constituent of certain high explosives. On heating with an excess of precipitated copper oxide gummy acids are formed, such as galactinic and pecto-galactinic acids compounds which are also formed from galactose. By oxidation with bromine lacto-bionic acid is formed, in which the COH group is converted into COOH. Potassium permanganate in acid solution oxidises it to carbonic acid, but the reaction is not complete, not more than 80 per cent. of the theoretical quantity of carbon dioxide being obtained. By heating with phenylhydrazine acetate two compounds are formed ; one of these—phenyl-lactosazone—is sparingly soluble in cold water, but in 80 to 90 parts of hot water, from which it separates on cooling in fine yellow needles melting at 200° C. with ‘decomposition. It is also soluble in alcohol and ether ; the latter CHEMICAL PROPERTIES OF MILK-SUGAR. 15 solvent extracts it from aqueous solution. The second compound is an anhydride of phenyl-lactosazone, and is almost insoluble in hot water; but can be crystallised from hot alcohol in yellow needles which melt at 223° to 224°C. Muilk-sugar is distinguished from other sugars by its osazone forming an anhydride. By treating with strong cold hydrochloric acid the phenyl- hydrazine groups are removed, and lactosone is formed. The relation between these compounds is shown by the following formulie :— sai Osazone. Osone, 6 H it H—C—ou hue ee C=0 ( oo = CH Hee / \ - GEES HO a H C=N—N® CHs The osone is readily reconverted into osuzone by treatment with phenylhydrazine acetate in the cold. By reduction with sodium amalyim a mixture of mannitol and dulcitol, hexahydric alcohols of the formula (;H,,O,, with lactic acid and methyl, iso-propyl and hexyl alcohols is formed, On heating with acetic anhydride and sodium acetate an oct- acetyl-lactose is formed. This crystallises in stout prisms from a mixture of alcohol and chloroform, and has an_ ill-defined melting point about 90° C. Its solution in chloroform is opti- cally inactive or very slightly levo-rotatory. Milk-sugar dissolves lime, baryta, lead, copper, and mercuric oxides, and probably forms compounds with them. No com- pound with sodium chloride is known, Ammoniacal lead acetate precipitates milk-sugar from an aqueous solution, It is not fermentable by ordinary yeast. and is unacted on by invertase, diastase, rennet, pepsin, and trvpsin. There ewists, however, an enzyme, which has been called lactase, which is found in fresh kephir grains, which hydrolyses it to glucose and galactose. The enzyme does not appear to be present in dried kephir grains, but is probably found in other sub- stances. The action of acids generally is to convert it into glucose and galactose. Nome organic acids, such as citric, are, however, without action on milk-sugar-when heated for moderate periods. Preparation.—Mlilk-suvar is prepared on a large scale by evaporating whey @ vacuo, after neutralisation of any acid with lime and clarification with alum or other means, and allowing it 16 INTRODUCTORY—THE CONSTITUENTS OF MILK. to crystallise. The product is purified by re-solution, treatment with animal charcoal and re-crystallisation. In countries where alcohol used for manufacturing purposes is free from duty the sugar is precipitated from solution by this means instead of being crystallised from water. : On a small scale it is best to precipitate the protein from milk or whey by as small a quantity of acid mercuric nitrate (p. 90) as possible. The clear filtrate is neutralised with dilute caustic soda solution till a very faint tinge is given with phenol- phthalein; it is filtered from the precipitate thus produced. which consists of mercury salts. Sulphuretted hydrogen is passed through the clear solution to remove the mercuric oxide dissolved by the sugar, and, after filtration from mercuric sul- phide, the sulphuretted hydrogen is expelled by boiling. On evaporating the solution, milk-sugar crystallises out; crystallisa- tion may be hastened by vigorously stirring the concentrated solution while it is being rapidly cooled. Glucose and Galactose.—These are two isomeric sugars of the monose type. Both are aldoses or aldehydrols, and have been obtained in three modifications («- and $-modifications and a stable equilibrium form). Their constitution is given by E. Fischer as Glucose. Galactose. COH COH n_l_on Ho H on—(—4 on_b_H u—b_on ou_l_u H_U_oH H_b_oH bat, OH oH, OH Wohl and List have confirmed the constitution of galactose. They are thus isomeric sugars differing only in the third asymmetric carbon atom from the aldehyde group. It is not known whether these sugars on solution in water give a constant rotation for a short time as in the case of milk- sugar. Their specific rotatory powers [«]p are Glucose. Galactose. Equilibrium form, . 2 SQFT 80-3° a-modification, 3 . » 105° 120° Bi-rotation ratio, . 3 ‘ 2 15 Both sugars give, on treatment with phenylhydrazine acetate, nearly insoluble osazones. Phenylglucosazone crystallises from dilute alcohol in fine yellow needles melting at 204° to 205° C. PRODUCTS, DERIVED FROM MILK-SUGAR. 17 to a dark red liquid: phenvlealactosazone is obtained in vellow needles from wlcoholic solutions, which melt at 188° to 191° C. with decomposition. They are converted into osones by treat- ment with strong cold hydrochloric acid. ; Products derived from Milk-Sugar.—The most important of these products is formed by the action of certain micro-organisms on milk-sugar during the so-called lactic fermentation. By their action the milk-sugar is split up into laetie or oxypropionic acid almost quantitatively, a certain portion, however, being con- verted into other products, of which carbon dioxide is the most important. The micro-organisms which produce lactic acid are acted on inimically by acids, so that not much more than 1 per cent. of lactic acid is usually formed, unless the solution is kept neutralised by chalk or other means. H Its formula is cH,—-¢_voon, and it contains an asymmetric On carbon atom: it is not, however, optically active, though the isomeric sarcolactic acid possesses this property. It appears to be w racemic compound; but both the dextro- and levo-acids are produced by certain micro-organisms. It has a remarkable tendency to form compounds which contain less water. On evaporating aqueous solutions of lactic acid, dehydrolactic acid is formed, C,H,,0., which, by further evaporation (especially ata high temperature), vives lactide, C,H O,. Lactic acid acts as a monobasic acid: while dehydrolactic acid behaves as a monobasic acid, monohydric alcohol and an ethereal salt at the same time: lactide is a neutral substance. Sarcolactic acid gives the same lactide, which, on boiling with water, is converted into the inactive modification. The so-called syrupy lactic acid is a mixture of lactic and dehyvdrolactic acids with probably a little lactide. Wislicenus has shown that by direct titration with alkali lactic, and dehydro lactic acids are estimated, while by further boiling with excess of alkali one molecule of lactic acid is produced for each molecule of dehydrolactic acid, and two for each molecule of lactide. Dehydrolactic acid has not been obtained pure. but appears to be amorphous and nearly insoluble in water. Lactide can be prepared by subliming ‘syrupy lactic acid at 15° in a current of dry air. It is insoluble in water, but can be crystallised from alcohol in colourless rhombic plates melting at 124°5°C. It boils at 255°C. Svrupy lactic acid is said to have a specific vravity of 12485. Lactic acid is not appreciably volatile in dilute solation, but «= 18 INTRODUCTORY—THE CONSTITUENTS OF MILK. passes over with water to a slight extent as the solution becomes concentrated. Lactic acid is soluble in and miscible in all proportions with water, alcohol, ether, and glycerol. It is insoluble in petroleum ether. Fats also dissolve it. It is probable that the lactic acid present in milk is, partially at all events, dissolved in the fat. As milk almost immediately after milking contains organisms which produce lactic acid, it may be considered as a normal constituent of milk ; indeed Béchamp has held that it is produced from milk by organisms (micro-zymes) derived from the udder itself. That this view is erroneous is shown by the fact that Lister, Pohl, Warington, and others have succeeded in preserving milk, drawn direct into sterilised vessels, for a considerable length of time without the development of acidity. Lactic acid probably exists in milk, not in the free state, but as a salt, at all events until the acidity is sufficient to curdle the milk on boiling. The Proteins—Properties.—Our present knowledge of the proteins of milk is far from complete, though much work has been done on the subject. This is due to the fact that it is extremely difficult to obtaim these compounds in anything like a state of purity. The method of crystallisation, which is so largely depended on in the case of other bodies, is only available in the case of albumin, and as proteins are altered in their essential properties by very many reagents, the choice of methods of purification is limited. The difficulty is still further increased by the peculiar behaviour of casein in retaining calcium salts, once it has been brought into contact with them, as is the case in milk. The proteins of milk have been prepared in as pure a state as possible by the general method of precipitating them by some reagent, dissolving them, reprecipitating as many times as may be thought necessary, and, finally, by eliminating such impurities as may have been introduced during the process. As there is no means of knowing when all the impurities have been eliminated, it is possible that we are yet unacquainted with the proteis of milk in a state of purity. This should not be forgotten during their study. The proteins are composed of carbon, nitrogen, oxygen, and usually sulphur and phosphorus. The exact mode of combination of the elements in any protein is not known but recent researches, notably by Hofmeister, Schiff, Citas, Kiihne, Neumeister, Hammarsten, E, Fischer, Abderhalden, Chittenden, Osborne, and Skraup, have thrown much light on the types on which proteins are formed. . Of the ultimate products obtained by the continued breaking down of proteins either by enzymes, acids or other hydrolysing hydrogen, PROTEINS—PROPERTIES. 19 agents, the most important, both in character and amount, are amino-acids; it has been found that nearly, if not quite, all the amino-acids obtained from proteins are «compounds of the type— NH, | NH,H * R—CH—COOH, or, better, R-C< \ H Coo. Amino-acids of this type have also formed the starting point in the synthesis of compounds having many of the characteristic reactions of proteins, and identical with those formed by their hydrolysis—the polypeptides. These acids condense readily to form what were called “ an- hydrides,” but which really have no anhydride grouping; the condensation takes place between the amino-sroup of one mole- cule and the carboxyl-group of another, and di-keto-piperazine compounds are formed, thus— NH, COOH NH—C'0 R—CH< + UHR, =R—-CHM >CH—R, + 20H). COOH NH, CO—NH By boiling with concentrated hydrochloric acid the hetero- cyclic compound is converted into an open chain. thus— NH, COOH NH—CO | | R—-CHS tht + UR, = -Uh—CO— Sh HR, CO—NH These compounds form the simplest polypeptides. By the action of an acid chloride on the silver salt of a polypeptide, or by the condensation of acid-azides with amino-acids, employed by Curtius, it was possible to link up three or more amino-acids ; or by protecting the amino-group of a polypeptide by the intro- duction of a carboxethyl-group Fischer was able to condense the carboxyl-group with an amino-yroup of another amino-acid, and by introducing an «halogen acid chloride into the amino- group and substituting an amidogen radicle for the halogen he was able to condense the amino-group with the carboxyl- group of another amino-acid. By these and other means polypeptides containing two, three, four, and five amino-acid radicles have been sy nthesised, and some of these have been identified with products of hydrolysis of proteins, or with their optical isomerides. There is little H,—00C * Or possibly R-C< ‘ H COO—-H.NC—R. 20 INTRODUCTORY—THE CONSTITUENTS OF MILK. doubt that the grouping—CH—NH—CO—CH—is characteristic of proteins; Fischer also considers it proved that the di-keto- piperazine group also occurs. : ey Fischer has recently prepared a polypeptide containmg 18 molecules of amino-acids; it was /-leucvl-triglycyl-d-leucyl- triglycyl-I-leucyl-octoglycyl-glycine, and gave many of the protein reactions; this compound was hydrolysed by trypsin, but not by pepsin. ; Classification of Proteins.—A joint committee of the Chemical and Physiological Societies has proposed the following classi- fication for proteins :— 1. Protamines. These are characterised by being free from sulphur, and containing large amounts of arginine. Strongly basic. 2. Histones. These are very basic substances, and are precipitated by ammonia. They contain little sulphur. Albumins. Soluble in water; coagulated by heat. Globulins and their derivatives. Insoluble in water, but soluble in salt solutions. . Sclero-proteins; insoluble proteins which form the supporting structures or connective tissues of animals. Phospho-proteins; derivatives of para-nucleic acid; do not contain purine or pyrimidine derivatives; are distinctly acid substances. Conjugated proteins, subdivided into— > Rk Be a (a) Nucleo- proteins; derivatives of nucleic acid; contain purine and pyrimidine derivatives. (b) Gluco- proteins; containing a carbohydrate radicle. Mucins. (c) Chromo - proteins; coloured protein substances as hamoglobin. The proteins of milk are :—- Class 3. Lactalbumin, . e . about 0-4 to 0-5 per cent. » 4 Lacto-globulin, . f . traces. 33 1D: Storch’s mucoid protein, . traces. » 6. Casein, . : . about 3-0 per cent. General Reactions of Proteins.—The following are the general reactions of proteins :— 1. The Biuret Reaction.—Add to a solution an excess of caustic alkali, and one drop of copper sulphate solution. Proteins give a violet colour, and proteoses and other products of hydro- lysis a reddish tint. : .This reaction is characteristic of proteins, 2. The Xantho-protein Reaction.—On heating with strong nitric acid proteins yield a yellow colour, darkened by alkales. This reaction is due to the presence of homocyclic ring compounds, chiefly tryptophane and tyrosine, and to a less degree by phenyl- alanine. REACTIONS OF PROTEINS. 21 3. Millon’s Reaction.—On adding Millon’s reagent (a solu- tion of mercurous and mercuric nitrates in nitric acid) to a protein a red colour is produced. This is produced by all oxy-phenyl compounds, and is given by the tyrosine group in proteins. +. Adamkiewicz’ Reaction.—Qn dissolving proteins in glacial acetic acid, and adding strong sulphuric acid coloured rings are formed at the junction of the two liquids. This reaction is due to the presence of vlyoxylic acid in the acetic acid, which compound gives a blue or bluish-violet colour with tryptophane. Hopkins and Cole, to make the test more certain, add glyoxylic acid, 5. Lieberman’s Reaction.—Proteins which have been ex- tracted with ether give a blue or bluish-violet colour on boiling with strong hydrochloric acid. This reaction is really the same as the above, as it is due to the presence of vlyoxylic acid or other aldehydic compounds in the ether. 6. Ehrlich’s Diazo Reaction.—Qn adding a diazonium salt to a soluble protein, and making alkaline, a red colour is pro- duced, if histidine or tyrosine be present in the molecule. A diazotised solution of sulphanilic acid is convenient. Other radicles give a yellow colour. 7. Richmond and Miller’s Diazo Reaction.—(n diazo- tisiny a solution of a protein, and adding an alkaline solution of 3-naphthol, a colour (usually yellow) is produced, and gas is given off in the cold. This test proves the presence of aryl and acy] amino-groups respectively, 8. The Halogen Reaction.—Chlorine and bromine sive insoluble compounds with all soluble proteins. Iodine gives a brown coloration. 9, Aldehyde Reactions.—Qn adding a solution of formalde- hyde to a solution of a protein neutral to phenolphthalein it becomes acid. This is characteristic of «amino-acids, the basic amino-group being converted into a very feebly basic methvlene- amino-group. 10. Ehrlich’s Aromatic Aldehyde Reaction.— Certain aromatic aldehydes when added to proteins in acid solution vive a well-marked coloured condensation product. p-dimethyl- amino-benzaldehyde and vanillin (p - hydroxy - - methoxy - benzaldehyde) give a red colour (the latter, however, tinged with blue) and p-nitro-benzaldehyde a green colour. This reaction appears to be characteristic of the tryptophane radicle. 11. On boiling most proteins with an alkali, a portion of the sulphur is transformed into sulphide, which may be conveniently demonstrated by the black colour viven on adding a solution of a lead salt. 22 INTRODUCTORY— TIE CONSTITUENTS OF MILK. The presence of protein may be considered as proved if re- actions 1, 8, and 9 are given; many, though not necessarily all, of the other reactions will also be obtained should proteins be present. Propucts or Hypronysis OF PROTEINS. By the action of hydrolysing agents—acids, enzymes—proteins are gradually split up into simpler compounds. These are classified as :— (a) Meta-proteins. Products which have undergone but little change and still have most of the protein characters; the product formed by heating lactalbumin in slightly acid solution to its coagulating point comes under this class. The curd formed by the action of rennet on casein will also come under this heading, and may be termed meta-casein (the usual name is para-casein). (b) Proteoses, which may be again subdivided into— 1. Proto-proteoses. Insoluble in ammonium sulphate solution, 24 to 42 percent., saturated. Hetero-proteose contains phenyl-alanine, proline, and glycine, but is free from tyrosine and tryptophane. Insoluble in 32 per cent. alcohol. Hemi-proteose contains tyrosine and tryptophane. Soluble in alcohol. 2. Deutero-proteoses A. Insoluble in ammonium sulphate solution, 54 to 62 per cent., saturated. May be further fractionated by their solubility in alcohol. 3. Deutero-proteoscs B. Insoluble in ammonium sulphate, 70 to 95 per cent., saturated. Those soluble in alcohol contain no sulphur. Those insoluble in alcohol contain sulphur. 4. Deutero-proteoses C. Insoluble in saturated ammonium sulphate solution and acid. Free from sulphur. (c) Peptones. Soluble in saturated ammonium sulphate solu- tion and acid. Those insoluble in 96 per cent. alcohol contain no tyrosine nor tryptophane. Those soluble contain both these substances. (d) Polypeptides, subdivided into— 1, Kyrins. Rich in basic substances—lysine and arginine. 2. Peptides. Simple condensation products of amino-acids. Diketo- piperazines. (¢) Amino-acids obtained on continued hydrolysis. This classification is not quite satisfactory, as the distinction between the various classes is somewhat arbitrary, and there is no sharp distinction between them. There is. however, a steady fall in molecular complexity. During hydrolysis, the hydrolysts ave not destroyed, or are destroyed with extreme slowness, and appear to be able to act on a relatively enormous quantity of the hydrolyte. The time PRODUCTS OF HYDROLYSIS OF PROTEINS. 23 taken to produce a given change on a given quantity of hydro- lyte is inversely proportional to the quantity of hydrolyst. Each hydrolyst has a certain optimum temperature at which it acts most rapidly, the action being diminished at both higher and lower temperatures. Certain substances—e.y., acids—affect the rate of hydrolysis by enzymes; their influence, however, follows laws which are not fully known. This may be perhaps due to the hydrolysing effects of the acid combined with those of other hydrolysts taking a course influenced by both of them. Fischer separates the amino-acids obtained by long boiling with acids by esterifying, crystallising out the glycine ester, and dis- tilling the others 7m vacuo, and extracting with ether. Fischer and Bergell also convert the amino-acids into their $-naphthalene sulphonates, which are very slightly soluble. These methods involve, however, some loss, but they give a rough estimate of the proportions of the amino-acids. A large number of amino-acids have been separated from the products of continued hydrolysis of proteins; these are— A. Mono-amino-mono-carboxylic acids. Amico-acetic acid, or glycine. Amino-propionic acid, or alanine. Amico-butyric acid. Amino-valeric acid or valine. Iso-butyl-amino-acctic acid, or leucine. B. Hydroxy-mono-amino-mono-carboxylic acids. Hydroxy-amino-propionic acid, or serine. Tetra-hydroxy-amino-caproic acid. C. Mono-amino-di-carboxylie acids. Amino-succinic acid, or aspartic acid. Amino-glutaric acid, or glutamic acid. D. Hydroxy-mono-amino-di-carboxylic acids. Hydroxy-amino-succinic acid. Hydroxy-amino-subcric acid. E. Di-amino-mono-carhoxylie acids. «-8-diamino-propionic acid, «-e-diamino-caproic acid, or lysine. a-6-diamino-valeric acid, or ornithine. F. Substituted-mono-amino-mono-carboxylic acids. a-amino-é-guanidine-valeric acid, or arginine. a-amino-f-iminazoly|! propionic acid, or histidine. The constitution of arginine and histidine is as below :— Arginine. Histidine. meee i See CH, NH SH CH, ur, cht_xu, ut,—xu, | | COOH COOH. 24 INTRODUCTORY—THE CONSTITUENTS OF MILK. @-phenyl-a-amino-propionic acid, or phenyl-alanine. @-p-oxy-phenyl-a-amino-propionic acid, or tyrosine. Indole-amino-propionic acid, or tryptophane. This has the constitution a Hydroxy-diamino-mono-carboxylic acid. Tri-hydroxy-diamino-dodecanocic acid. H. Diamino-di-carboxylic acids. Diamino-glutaric acid. Diamino-adipic acid. I. Hydroxy-diamino-di-carboxylic acids. Hydroxy-diamino-sebacic acid. Dihydroxy-diamino-suberic acid, and probably others. J. Pyrrolidine compounds. a-pytrolidine-carboxylic acid, or proline. Oxy-pyrrolidine-carboxylic acid, or oxy-proline. Proline has the constitution CH,—CH, el CH, CH COOH \V/ NH K. Thio-amino-acids. Protein-cystine and stone-cystine. These are derived respectively from a-amino-f-thio-lactic acid, and u-thio-8-amino-lactic acid, and are represented by the following constitutions :— Protein Cystine. tone Cystine. ; = : NH, NH, | | a mn CH, CH, ona CH—NH, CH—S—S—CH | COOH COOH COOH COOH. Among other compounds obtained by the hydrolysis of proteins are :— *L. Purine bases. These are contained in the nucleo-proteins; they are — containing a pyrimidine and a glyoxaline (or imidazolyl) ring, us— Pyrimidine. Glyoxaline. Purine. N= ‘CH IN = °CH | | 2CH 5CH CH—NH _ se ee I l 2CH, | CH 3N — °CH C—N 3N — 3C — "N i It is not certain whether purine or pyrimidine derivatives occur in milk proteins. PRODUCTS OF HYDROLYSIS OF PROTEINS. 25 Four purine bases are obtained in which substitution occurs only in pyrimidine ring ; the-e are— Hypo-xanthine, . : ‘ . 6-oxy-purine. Xanthine, . : ‘ 2-6-dioxy-purine. Adenine, . : : ‘ 6-amino-purine. Guanine, . : . 2-amino-6-oxypurine. The nucleic acids are derivatives of purine bases, being compounds in which a phosphoric acid radicle is condensed in the 8 position. Uric acid, which is excreted by the kidneys, has the composition of 8-oxy-xanthine. *M. Pyrimidine derivatives. Three pyrimidine derivatives are obtained from the nucleo-proteins :— Uracil, 3 : : 2-6-dioxy-pyrimidine. Cytosin, . . 2-oxy-6-amino-pyrimidin«. Thymin, . 2-6-dioxy-5-methyl-pyrimidine. N. Glucosamine. H H OH H pele ts} | CH,(OH) —C—C—C—C— CoH | Te Fic OH OH H NH, is obtained from the gluco-proteins. Glycine. Monoclinic crystals, soluble in 4°3 parts cold water, Nearly insdluble in alcohol. M.P., 282° to 236° C., with dark purple colour, Best obtained by the action of ammonia on monc-chlor-acetic acid, or by the hydrolysis of elue. Alanine. Needles. Soluble in £6 parts cold water. Nearly insoluble in alcohol. May be prepared from 2 parts aldehyde- ammonia and 1 part hydrocyanic acid with excess of HCL Leucine. Volatilises at 210° to 220° C. without melting. or melts in a closed tube at 270° C. Moderately soluble in water, and crystallises in soft nacreous scales consisting of concentrically vrouped rhombic prisms. Serine. Bunches of monoclinic crystals soluble in 32 parts water at 10° and 24 at 20° C. Insoluble in alcohol. Active form polarises + 6, and the levo-form occurs in proteins. Aspartic acid. Prepared by the hydrolysis of asparagin, or it may be separated from beet molasses. Polarises to the left in water, and to the right in strong acids. Very soluble in hot water, and little so in cold. Glutamic acid. Rhombic-spheroidal-hemihedric crystals, melts with decomposition at 202° to 202°5° C. One part soluble in 100 parts water at 16° C.; less soluble in alcohol. May be prepared by heatiny casein with HCl and ZnCl. *It is not certain whether purine or pyrimidine derivatives occur in milk proteins. 26 INTRODUCTORY—THE CONSTITUENTS OF MILK. Tyrosine, C,H,,NO,, is an oxyphenyl derivative of amino- propionic acid. It crystallises in fine glistening needles usually grouped in bundles, soluble in about 150 parts of boiling water. It gives a red precipitate with a solution of mercuric nitrate containing nitrous acid, and is capable of forming metallic salts. By tryptic digestion more tyrosine is produced than leucine ; other hydrolytic actions produce greater quantities of leucine. — A. J. Brown and J. H. Millar have shown that tyrosine is separated in the early stages of tryptic digestion, but the tyrosine nucleus is very resistant to peptic digestion. Prorimate Determination of the Constitution of Proteins.— Hausmann’s method consists in boiling 1 gramme of protein with strong hydrochloric acid for some hours and determining 1. The nitrogen split off as ammonia by distillation with magnesia, preferably at a low temperature. 2. The nitrogen in the insoluble portion. Melanin nitrogen. 3. The nitrogen in the phospho-tungstic acid precipitate ; basic (lysine, histidine, or arginine) or diamino-nitrogen. 4. The soluble nitrogen. Mono-amino-nitrogen. The only milk protein which has been thus examined is casein, and the mean of the results of Giimbel, Osborne and Harris, and Kutscher is— Ammonia Melanin Diamino- Mono-anjino- Nitrogen. Nitrogen. Nitrogeu. Nitrogen. 1-63 0:27 3°87 9-98 The Proteins of Milk—The number of proteins present in milk (of the cow) has been variously stated at from one to eight by different observers. The most recent work has tended to reduce the number to not more than four, the larger number described having been obtained by faulty methods of separating these bodies or by the action of some reagent used on the protein. Many of the products described are now known to be mixtures of one or more of the proteins with various impurities, or decom- position products obtained during the separation of the proteins one from another. The theories of leading observers are briefly given as follows :— Duclaux maintains that there is only one protein in milk, which exists in two forms—the coagulable and non-coagulable ; he gives to this protein the name of casein. The first modi- fication is not in a state of solution, and can be separated by filtration through a porous jar; it is combined with the phos- phates of the alkaline earths, and this causes it to differ in its properties from the other modification, which is in a state of true solution and passes through the porous jar. Were this view correct, the coavulable modification should gradually lose its distinctive properties as it is purified from phosphates; and, on PROTEINS OF MILK, QT. the other hand, the non-coagulable modification should be capable of being converted into the other by associating it with phosphates ; neither alternative has as yet been found possible, and, as two proteins having distinct properties can be separated from milk, Duclaux’s view is hardly tenable. Hammarsten describes two proteins; one, casein, corre- sponding to Duclaux’s coagulable casein; the other, lact- albumin, corresponding to Duclaux’s non-coagulable casein. He shows that lactalbumin has the properties of a true albumin, approaching very closely to serum-albumin, but differing from it in certain physical constants, which entitles it to rank as a distinct body. Sebelein has shown that there exist in milk traces of a globulin, in addition to the casein and albumin of Hammarsten. Halliburton describes the proteins of milk as caseinogen and lacto-albumin; there is no essential difference between the casein of Hammarsten and the caseinogen of Halliburton, except a difference of name. He reserves the name cascin for the curd produced by the action of rennet. Hewlett has confirmed Sebelein’s statement as to the existence of globulin in milk, though he has shown that Sebelein’s globulin was probably contaminated with small amounts of casein, Musso and Menozzi have claimed the presence in milk of a body midway between casein and albumin: this is probably the globulin of Sebelein in an impure state, as their description is in fair accordance with a statement of the properties of the latter. Radenhausen and Danilewsky have described many proteins in milk. Hammarsten and—later—Chittenden and Painter have shown that their view that casein is a mixture of two compounds is untenable, while the various lacto-protein bodies have been shown to be the result of their method of separating casein and albumin. Wynter Blyth has described a body called galactin in milk ; this is essentially lacto-protein, perhaps contaminated with some organic salts, and has no real existence in milk, beine portions of the casein and albumin which had escaped separation, tovether with products of their decomposition during the process used for their removal. Béchamp supposes that the proteins of milk number thiee —casein, albumin, and a body having the properties of an enzyme, which he calls galacto-zymase; this enzyme he finds liqueties starch paste, evidently not its normal function in milk : his results have not been confirmed. He also supposes the casein and albumin to exist in milk in combination with bases (soda, lime. or potash). 28 INTRODUCTORY—THE CONSTITUENTS OF MILK. Biel has described syntonin as a normal constituent of milk, but the existence of this must be considered doubtful at present. Palm has stated that albumoses are found in milk; this is probably not wholly correct; it is possible that traces of albu- moses are formed during the decomposition to which milk is prone, but no other observer has identified more than traces, while Palm gives 15 per cent. as occurring in milk. True peptone has been proved to be absent. Storch’s researches have been referred to (p. 2). Babcock has found very small amounts of nuclein, but the presence of this has now been disproved, and the same observer has with Russell separated a proteolytic enzyme. There are also a peroxydase, a catalase, and a reductase. From the above list of the various proteins described as existing in milk we may select the four of whose existence we have the strongest evidence ; these are casein, lactalbumin, lacto-globulin, and Storch’s mucoid; the last two, however, are only found in traces in milk, and, practically, the proteins may be reduced to the former two, The other compounds described, except the enzymes whose proteinic nature is not fully established, are hypothetical. The main reactions that distinguish the four proteins of milk are as follows :—Casein is precipitated by saturating the solution with sodium chloride, magnesium sulphate, and ammonium sulphate; globulin is soluble in a saturated solution of sodium chloride, but is precipitated by magnesium and ammonium sulphates ; albumin is soluble in saturated solutions of sodium chloride and magnesium sulphate, but is precipitated by satura- tion with ammonium sulphate, while Storch’s mucoid is not in solution; albumin is, however, precipitated from a saturated solution of magnesium sulphate by acidifying slightly, and is redissolved by neutralisation of the solution. Casein and globulin are precipitated by the addition of acid, while albumin (and globulin, if much salt is present) is not so precipitated. Casein has the remarkable property of being acted on by chymase, the enzyme of rennet, with the formation of an insoluble pro- duct; albumin is coagulated by the action of heat, the raising of the solution to about 70° C. under suitable conditions of acidity being sufficient to precipitate a vreat portion. Casein is gradually removed by filtration through paper, and com- pletely through coarse porcelain; filtration through fine por- celain removes all the proteins. Properties common to the three protems are solubility in alkalies, insolubility of their copper, mercury, and other salts, insolubility in alcohol; all are precipitated by tannin and phospho-tungstic acid. Casein.—This protein, when pure, is a white amorphous CASEIN. 29: body without taste or smell: it is practically insoluble in water. dissolving in this menstruum to the extent of about 0°1 per cent. : it is quite insoluble in alcohol and ether. Very dilute acids seem to diminish the solubility; but it is soluble in stronger acids. becoming, however, changed; a solution of casein in acetic acid has been used as glue; it is completely soluble in caustic alkaline solutions even when very dilute; the solutions of the carbonates, bi-carbonates, and phosphates of the alkalies also dissolve it. and from these solutions, as well as those of the alkalies, it is pre- cipitated unchanged by the addition of sufficient acid to neut- ralise the alkali. It has the property of forming an opalescent solution when it is dissolved in the least possible excess of sodium phosphate, and the addition of small quantities of calcium chloride is made; it gives then a solution having the appearance of milk. It is highly probable that milk contains casein in this form. Casein has a peculiar affinity for calcium salts, especially the phosphate. It is extremely difficult to free it from tlus body, the purest preparations that have been prepared having always been contaminated with small amounts of this compound. Case yields a comparatively small amount of sulphide if boiled with an alkali, and contains less of this element than cither globulin or albumin; it also differs from these compounds by containing phosphorus; on analysis, like other proteins, it docs not. yield very concordant results; the most probable com- position is as follows :— Per cent, 1 Per cent. Carbon, . ; . 5313 Sulphur, ‘ O77 Hydrogen, . 4 7:06 j Phosphorus, (PSG Nitrogen, ; . 1578 Oxygen, . 2240 The composition of casein is variously stated by different authorities. The following are the most reliable results :— | . : I | ‘ Authority. , eae ee ee “Stlian Lehmaun. | ae I Per cent. Percent. | Percent. Percent. Percent. | Per cent. C 52:96 . 33:30 53-07 S408 54-00 54-22 H TOS rours 7-13 7-09 7-04 TAT N 15-65 15-91, 15-64 15°57 15-60 | 15-49 F Ss O72 O-S2 0-76 OTT OTT 0-91 P O85 O87 0-80 ft 085 | oO 22°08 | 22-003 22:60) en 21-70 t The author has calculated the two following formule as possible for casein; the first agrees with the results of Hammarsten, Chittenden and Painter, and Ellenberger, while the second 30 INTRODUCTORY—THE CONSTITUENTS OF MILK. represents the figures obtained by Stohmann, Lehmann, and Ritthausen ; it is probable that the last three observers did not remove Storch’s mucoid protein so completely as the others :— I, ; II. | Cig2He5sN qi SPO52. Chey Hea N ae5P951- | ; Per cent. | Per cent. C | 52-96 54-04 H 7:03 i 7-10 N | 15-64 15-56 | Ss ot 0-86 0-84 P | 0:84 i 0-82 6) | 22-4] 27-0 Hammarsten and Chittenden purified their casein by solution in alkali and reprecipitation several times; Ritthausen worked on the copper salt; and Lehmann used what he designated ““ genuine ”’ casein, which was separated from milk by the use of a porous plate. Lehmann found that in “ genuine’ casein 1°45 to 1°75 parts of lime were combined with 100 parts of casein; one molecule CaO to one molecule C,,.H.,.N,,SPO,. requires a proportion 153. Sdldner has also shown that two lime compounds exist containing 1°55 and 2°39 per cent. CaO respectively, which correspond with CaO and 1°5 CaO to one molecule of casein. 66 N : . The author has found that T00 sodium and potassium carbonate solutions treated with an excess of casein dissolve 1:86 and 1:83 parts per 100 ¢.c. respectively. The first formula would give 1:84. It appears probable that casein exists in milk as a calcium sodium salt combined with one molecular proportion of tri- calcium phosphate. The author has found that by filtration through a porous cell the compound separated has the com- position :-— Calculated for 0-477 °/, N and Ci g2HessN qi SPO 59 CaNa : i(Ca3P20s). Casein nitrogen, 3 O-477 r CaO, - - : ‘ 0-116 0-119 P.O., ‘ . ‘ ‘ . 9-123 0-121 Alkalies, . ‘ ‘ . . 0-031 0-026 Total ash, . - : 3 . 0:27 0-266 It was also found that on adding 8-6 e.c. of normal hydro- chloric or sulphuric acid per litre the casein was precipitated on boiling, and the acidity of the serum was equal to the acidity of the milk after boiling. The quantity of acid required by the CASEIN. 31 above formula to replace the atom of sodium by hydrogen in the above formula is 8-3 ¢.c. The precipitated casein contained all the lime and phosphoric acid, the quantities carried down being (calculated as before for 0-477 nitrogen)— CaQ, 0-120 P,O,, : 0-120 Total ash, . . O23 From the above figures it is seen that the formula given fairly well represents the composition of casein, though, of course, it is only an approximation; the real formula is almost certainly a multiple of this. lt is noticed that the swphur is lower than that calculated from either of the above formule. By treating casein with alkalies a portion of the sulphur is removed as sulphide. It is possible that in the purification of the casein by solution in dilute alkali and precipitation by acids that a small amount of decomposition sets in. The following are the amounts of various acids (calculated as e., of normal solution per litre of milk) required to precipitate the casein on boiling :— Hydrochloric and sulphuric, Si ee. Acetic and lactic, ‘ 9 to LO ec. Citric; ‘ ‘ ‘ 135 ce. Oxalic, . ‘ 28-5 cc. Phosphoric, —. : : 34 to 35 e.c. That large amounts of the weaker acids are required is only to be expected ; the behaviour of oxalic and phosphoric acids is anomalous, and appears to be due to the fact that oxalic avid removes the lime from the cassin complex, while phosphoric acid forms an acid phosphate with the tricalcium phosphate. In either case the formation of a mono-acid calcium salt of casein combined with calcium phosphate is prevented. Revis and Payne consider that casein exists In milk com- bined with calcium phosphate, and that on acidifying the milk with small progressive amounts of acid the calcium phosphate is removed from the combination; when the casein is precipi- tated by the acid practically all the calcium phosphate is pre- cipitated. Their results show that calcium is removed from the complex in direct proportion to the acid added, but their figures with regard to phosphoric acid are less definite. They also show that it is very improbable that any appreciable amount. of lactates of casein are formed in milk as it turns sour, as supposed by van Slyke, Hart, and Laxa. Casein behaves-as a tribasic acid; it has also basic properties, and combines with acids giving salts easily decomposed by water. The acid functions are much more strongly marked than the 32 INTRODUCTORY—THE CONSTITUENTS OF MILK. basic ones. On hydrolysis it ultimately yields, according to Fischer and others, especially Osborne and Greed, the following (the estimations of leucine, glutamic acid, tyrosine, lysine, arginine, and histidine are probably nearly correct; the other figures probably low) :— Glycine, none Alanine, 15 Leucine, a 10°5 Phenyl-alanine, 3-2 Proline, 6-7 Glutamic acid, 10-50 Aspartic acid, 1:39 Cystine, 0-065 Serine, 0:43 Oxy-proline, 1-5 Tyrosine, 4:5 Lysine, 58 Histidine, 2°6 Arginine, . 4:84 Tryptophane, ‘ 15 Ammonia, 2 ; ' ‘ ¥ 1-6] Cystein, . : h : . none Amino-valeric acid, . . ‘ . ee Glucosamine, $ 3 : . none Diamino-trioxy-dodecanoic acid, » O75 Levites has also shown that casein contains 0-93 per cent. of nitrogen removed by the action of nitrous acid—v.e., as free NH, group—this compound, however, yielded as much nitrogen as ammonia (1°67 per cent.) as the original casein. When dissolved in dilute alkali it has a levo-rotatory action on polarised light. J. H. Long gives the specific rotation of casein when 5 grammes are dissolved in 100 c.c. of water with the ; N det number of c.c. of T0 alkali given as follows :— ) NaOH, . . 22-5 — 952° i ; : 45-0 —103-5° i . . 675 —107-6° ii . 90 11s? KOH, ; . 45 — 1044 LiOH, 22:5 — 94-8° 7 . 45 — 100-8" NH,OH, . : . 45 — 97-8? It is completely precipitated {rom milk by copper sulphate ; if the solution be neutral, a definite compound containing about 1 per cent. of copper is obtained ; basic compounds are probably obtained if the solution be alkaline. Mercury salts precipitate casein completely, even in acid solution; it is also precipitated by meta-phosphoric acid. Casein has probably a higher mole- cular weight than the other proteins existing in milk. CASEIN, 33 On boiling milk with the quantity of acid just sufficient to curdle, the whole of the casein is not precipitated ; thus the author found that 2°91 per cent. was thrown down out of a total of 3°05 per cent. Casein on treatment with strong sulphuric acid gives off carbon monoxide. Preparation of Casein.—Casein is prepared from milk by diluting it to about five times its volume, and adding sufficient acetic acid to give 0-1 per cent. of the acid in the solution; the casein is precipitated, carrying down with it the fat: the pre- cipitate is well washed by decantation some ten times, collected on a cloth filter, washed on the filter, and then dried, as far as possible, by pressure. This precipitate is dissolved in the least possible excess of ammonia, the solution allowed to stand for some time (to allow the fat to rise), then syphoned off and filtered, and the filtrate precipitated, as before, by acetic acid; the precipitate washed and redissolved in ammonia; and this treat- ment repeated three or four times. The cascin is now rubbed up in a mortar with 80 per cent. alcohol, and the alcohol poured off; the treatment with alcohol is repeated several times, using. finally, absolute alcohol; it is then treated two or three times with ether which has been freshly distilled from some reagent which removes aldehydes (e.7., casein. sodium phenyl-hydrazine- sulphonate) in the same manner, and then extracted for some hours in a Soxhlet extractor to remove the fat, and the ether evaporated off at as low a temperature as possible, This casei may. tf a very pure product is required, be redissolved, repre- cipitated, and the treatment with alcohol and ether repeated ; the casein is finally dried at 100 to 105- C., and is then a white amorphous powder: if casein containing water is dried it forms horny masses. Products of Hydrolysis of Casein.—The following composition is given by Chittenden and Painter to the products of hydrolysis of casein :— CASEOSES PRODUCED BY THE ACTION OF PEPSIN. i = > | ; Proto-Caseuse, Deutero-Casenses. 1 I | Dys- | | Caseose. | Weak | Sttong Nis e Pepsin. - Pepsin. Mixed. ; - 2 | | Casein. | fairies! ‘Per cent. | Per ¢ cent Percent. , Per cent. | Percent. Pere cent. Per cent some S830 | SLI | S289 | 5440 | G19 1 5220 ' 47-61 bo ROT” TO 2 CO acOd 705. 694 675 | 1691 ° 1SBL | 1694 S84 | 1600 | 15-95 15°95 | 0°82 O72 VIS 0-95 BEd. O-87 | none , s ia 9 Do0R WTA | = H ‘ 34 INTRODUCTORY—THE CONSTITUENTS OF MILK. CASEOSES PRODUCED BY THE ACTION OF TRYPSIN. Casein. grea stp Caseone. Per cent. Per cent. Per cent. Per ceut. Cc 53°30 56°17 53°56 50°28 H 7:07 6-90 6°70 6°53 N 15°91 14°80 15:07 15°95 8 0°82 aa 0:93 0:78 * CASEOSES PRODUCED BY THE ACTION OF ACIDS. ‘ | Casein. Dys-caseose. | Proto-caseuse. | o Dente 2 pees i 2! Per cent. Per cent. Per cent. Per cent. Per cent. C 53°30 54°40 56°20 54°55 52°93 H 7:07 6 80 7:08 6°84 6:87 N 15°91 14°80 15°36 15°33 15°66 Siegfried has prepared a caseino-kyrine by restricted acid hydrolysis. It has the composition C,,H,;N,O,, and on further hydrolysis yields 1 molecule of arginine, 2 of lysine, and 1 of glutamic acid. be a mixture. Skraup and Witt, however, consider this to CASEOSES PRODUCED By THE AcTION OF RENNET. Hammarsten gives the following composition for the curd produced by rennet, and the caseose of the whey :-— Curd Whey Caseose. Found. Caleulated Found. Calculated. Carbon, 52-88 52-95 ASS 49-72 Hydrogen, 7-00 7-00 7:00 6-97 Nitrogen, . | 15-84 15-88 13-25 13-18 Phosphorus, 0-99+ 0-98 From these figures the author has deduced formule, not as * The figure 0-68 occurs in the original ; evident that 0-78 is the correct figure. + Determined by the author. from the weighings given it is CASEOSES. 35 absolutely correct, but probable near approximations. They are :— Curd, : ; . » Cy HooNy,SPO,, Whey caseose, CoH yN5045 The curd produced by rennet (calculated for 0-477 casein nitrogen, cf. p. 30) contains :— Calculated. Nitrogen, : e . O41 0-419 CaO, i 5 : . 0-119 0-119 P2055, 3 : : .» O-117 0-121 Ash, r ¥ ‘ é . 0:23 0-24 and the quantity of caseose nitrogen left in the whey is 0-061 J0538 The acidity of the whey was found to be 8-4 c.c. of normal alkali per litre less than that of the milk. These figures are in accordance with the view that casein in milk, C,,.H,..N,,8PO,,CaNa . 3(Ca;P,0,), is split by rennet into— Cy sp Hoon NaS POs Ca . $(Ca,P,0,) (curd) and C,H; N,O\, (whey caseose). The whey caseose is free from tyrosine and tryptophane. When acted on by lactic acid the curd protein forms lactates, which have the property of becoming stringy when heated. Tf calcium be removed from milk the action of rennet differs, and a whole series of cascoses is formed, and no curd is produced. Casein and its immediate derivatives appear to have the power of forming with tricalcium phosphate very insoluble salts. Reactions of the Caseoses. Dys-caseoses.—These products in the pure state are soluble in water; they combine with calcium salts, especially phos- phates, to form insoluble compounds. The following reactions are given by dys-pepto-caseose ; the other dys-caseoses behave similarly. Acetic acid in moderate excess gives an insoluble white pre- cipitate, soluble in large excess on heating. Hydrochloric and sulphuric acid give precipitates, also soluble in large excess on heating. Even 0-2 per cent. hydrochloric acid produces complete precipitation. Nitric acid gives a precipitate far more easily soluble in excess of acid. On warming, the solution turns yellow, and, with ammonia, gives the orange-yellow colour of the xantho-protem reaction. With a little copper sulphate and an excess of caustic potash the violet colour of the biuret reaction is given. 36 INTRODUCTORY—THE CONSTITUENTS OF MILK. Cupric sulphate and ferric chloride precipitate dys-caseose. Ammonium sulphate added to saturation precipitates dys- caseose, but sodium chloride does not. Addition of acetic acid, however, to the salt-saturated fluid gives the usual precipitate of dys-caseose. : The insoluble compound with lime salts is dissolved with more or less readiness by an alkaline trypsin solution, giving finally a caseone, presumably trypto-caseone. Proto - caseoses.—Proto-caseoses are soluble in water, and precipitated incompletely by the addition of acetic, hydrochloric, sulphuric, and nitric acids. They are soluble in 0-4 per cent. hydrochloric acid, but are precipitated by stronger solutions. The portion not precipitated by acetic acid gives a precipitate on saturation with salt solution and with potassium ferrocyanide. Copper sulphate gives a heavy precipitate, as does ferric chloride, but the latter is soluble in excess of the reagent. They give the xantho-protein reaction with nitric acid. Proto-caseoses are precipitated by saturation with sodium chloride. «-Deutero-caseoses are soluble in water, not precipitated by acids nor by saturation of a neutral solution with sodium chloride ; on adding acetic acid to the salt-saturated solution, «-deutero- caseose is incompletely precipitated ; it is precipitated by satu- ration with ammonium sulphate in the cold. #-deutero-caseose is precipitated by saturation of the solution with ammonium sulphate and boiling. Cupric sulphate gives a precipitate with «-deutero-caseose soluble in excess, but none with 3-deutero-caseose. Potassium ferrocyanide in acetic acid solution gives a preci- pitate with both deutero-caseoses. Caseone.—Only the trypto-caseone has been prepared ; it is not precipitated by acids: nor by saturation of its solution by sodium chloride ; nor by ammonium sulphate, even on boiling ; nor by zinc sulphate. Caseone and peptones generally are very hygroscopic. Caseone is dialysable and only precipitated by such reagents as tannin and phospho-tungstic acid. All the caseoses and caseones give the biuret reaction with copper sulphate and caustic potash. It must be remembered that the separation of the caseoses is by no means sharp: thus proto-caseose is not completely preci- pitated by sodium chloride and the residue is obtained with the a-deutero-caseose. Besides the above products another caseose, resembling proto- caseose, but soluble only in dilute acid and galt solutions, is also formed ; this is called hetero-caseose and is precipitated by dialysis. LACTALBUMIN. 37 Lactalobumin.—This protein has the property characteristic of albumins of being coagulated by raising the temperature of its solution to 70° C.; the precipitation is never complete, since as much as 12 per cent. may be left in solution, according to Sebelein. Lactalbumin, like other albumins, is not precipitated by saturating its solution with magnesium sulphate; but on the addition of acetic acid to the solution a precipitate of albumin is obtained, and this is redissolved on neutralisation of the acid. It can be obtained in a crystalline form by diluting the saturated magnesium sulphate solution with an equal bulk of water, adding acetic acid till permanently turbid, and setting aside. (sentle shaking assists the crystallisation. It is, like other albumins, precipitated by sodium sulphate added to saturation, and also by ammonium sulphate. It is also precipitated ly tannin, phospho-tungstic acid, and other general reagents. The salts of albumin with copper, mercury, and lead are insoluble. Alcohol precipitates it and the precipitated albumin is soluble in water. It has a specific rotatory power [@]p of — 67-57 (Léchamp). Lactalbumin has the following composition, according to Sebelein :— Per cent. Per vent, Carbon, . 52-19 Sulphur, . 1-73 Hydrogen, . 718 Oxygerf, . 5 23-13 Nitrogen, 15-77 It differs from casein by containing no phosphorus and about twice as much sulphur. When boiled with an alkaline solution of lead acetate it wives a very strong sulphur reaction. There appears to be no difference in elementary composition between soluble and coagulated albumin. Abderhalden and Hunter state that the mixed coavulable proteins of milk contain 1-2 per cent. of elycine. Preparation of Lactalbumin. — Milk is saturated with magnesium sulphate and filtered. To the clear filtrate is added as much acetic acid as will give 1 per cent. of acetic acid: lact- albumin is precipitated, and is filtered off. The precipitate, with the filter, is stirred up with water, and the acid neutral- ised: the lactalbumin dissolves. The solution is filtered, and reprecipitated by saturating with magnesium sulphate and adding } per cent. of acetic acid; this is repeated three or four times: the solution of lactalbumin is then dialysed to remove salts, The solution is precipitated by alcohol, the precipitate washed with alcohol and ether and, finally, dried at a low tem- perature. Lactalbumin, prepared in this way, is a white powder without taste, and completely soluble in water. The albumoses are bodies analogous to the caseoses; they are 38 INTRODUCTORY—THE CONSTITUENTS OF MILK. not, however, precipitated by acids, and are less readily preci- itated by copper sulphate. Taato. Gis puine his protein is coagulated by heat and precipitated by neutral sulphates, tannin, etc.; rennet does not coagulate it. It coagulates at 72° C. It only occurs in traces in milk, but in larger amounts in colostrum. It is not known whether it differs chemically from serum-globulin. Its chief characteristic is its solubility in sodium chloride solutions even when acidified. ; Storch’s Mucoid Protein.—The following properties are given by Storch:—Washed with alcohol and afterwards with ether, and dried in air at the ordinary temperature, it forms a loose, fine, hygroscopic powder of a greyish-white colour. It is insoluble in dilute ammonia and acetic or hydrochloric acids ; it swells considerably without dissolving in weak solutions of alkahes, and is only partly soluble in dilute potassium or scdium hydroxide. It gives the reactions of proteins—z.e., red color- ation with Millon’s reagent, brown colour with iodine and yellow with nitric acid and ammonia (xantho-protein reaction). When heated with dilute hydrochloric acid it yields a substance which reduces Fehling’s solution; the amount of copper reduced is 6°5 parts for each 100 parts of dry ash-free substance. It gives also the biuret reaction. It contains 14-76 per cent. of nitrogen and 2-2 per cent. of sulphur, of which only a small portion is removed by boiling with alkalies. Preparation of Mucoid Protein.—(i.) The author has found the easiest method is to centrifuge sweet butter milk and wash the deposit several times with water made faintly a!kaline with ammonia, the deposit being separated each time by centri- fugal action. The mass is treated with strong alcohol, and after- wards with ether, and dried in vacuo. (u.) Storch has prepared it from butter, by melting 1 to 2 lbs. at a low temperature; the fat is carefully decanted; and the liquid rinsed twice with benzene, diluted with distilled water and mixed with one and a half times its volume of strong alcohol. The precipitate is washed with 60 per cent. alcohol and extracted with ether till all fat is removed, and air dried. (iii.) Fresh cream (about 30 per cent. fat) is diluted with four times its volume of a 33 per cent. solution of cane sugar and placed in a large separating funnel; after a day's repose, the sugar solution is drawn off, and the remaining cream again mixed with four times its volume of the sugar solution: this process 1s repeated four times and the washed cream is shaken with an equal volume of strong alcohol, and twice as much ether -and some benzene are added. A gelatinous precipitate separates MINERAL CONSTITUENTS. 39 from the clear ethereal solution, which is separated by filtration, washed with strong alcohol and afterwards with ether, and dried in the air at the ordinary temperature. Storch found that if the cream was mixed with water at 35° C. and separated in a cream separator, and this process repeated several times, the protein could be prepared from the washed cream. This method was, however, more difficult than that involving the use of cane sugar solution. The density of the mucoid substance containing 6°42 per cent. of mucoid protein and 1-03 per cent. ash was found to be 1:0228 at 15° C. This substance appears to he identical with a product described some years ago as f-casein by Struve; he separated it from his a-casein by dissolving in ammonia, when the @-casein was left; it was found in traces only in milk. Mineral Constituents.—On burning milk a white ash is left : this contains the mineral constituents of milk, altered, however, to some extent by the oxidation of some of the compounds present in milk ; thus the phosphorus and sulphur of the proteins give rise to phosphoric and sulphuric acids ; and carbon dioxide is also formed bv the oxidation of organic carbon. The ash does not truly represent the mineral constituents of milk. The averave composition of the ash of milk is— Per cent Lime, . ¥ ‘ . ‘ ye, Magnesia, i : s 2-80 Potash, . esTl Soda, . é é 667 Phosphoric avid, 2°33 Chlorine, 14-00 Carbon dioxide O-n7 Sulphuric acid, . - ‘ trace Ferric oxide, &e., ; 7 On 103-15 Less O = Cl, Ses 100 Hy The amount of insoluble ash—.e., ash insoluble in hot water— amounts to about 0:52 per cent. of the milk; and the soluble ash to 0-23 per cent. The soluble ash consists mainly of the chlorides of the alkalies, with a little carbonate and a mere trace of phosphates. The insoluble ash is mainly composed of double phosphates of the formula CaKPO,, the lime being partially replaced by magnesia and the potash by soda: double carbonates of the formula CaNa(CO.,), also exist in traces: these compounds are insoluble in water, and this accounts for the fact that the insolul.lr ash is always higher than the sum of the calcium and magnesium phosphates. 40 INTRODUCTORY—THE CONSTITUENTS OF MILK, An ash of this composition is only formed when the milk is homogeneous; if it is curdled, by natural souring or by the addition of acids, the precipitated lumps do not contain sufficient alkali metals to form these compounds, and much calcium and magnesium phosphates are formed; on dissolving in water, soluble alkaline phosphates go into solution, and calcium and magnesium phosphates, together with varying proportions of double phosphates, are left insoluble. Curdled milk gives the same total proportion of ash as fresh milk, but the soluble ash is higher and the insoluble ash lower. About 8 per cent. of the phosphoric acid present in the ash is derived from the phosphorus of the casein ; the traces of carbonic acid present are not true mineral constituents of the milk. Deducting these, we have a considerable excess of bases over acids; in the milk these bases are combined partly with the proteins to form soluble salts, and partly with citric acid to form citrates. Citric acid is contained in milk to the extent of 0-1 to 0-15 per cent.; its most characteristic salt is the calcium citrate, which is fairly soluble in cold water, but insoluble in boiling water. It is a tribasic acid, and forms three classes of salts. Séldner deduces the following composition as most probable for the salts existing in milk :— Per cent. Sodium chloride, NaCl, . ‘i P 3 . 10°62 Potassium chloride, KCl, . : ‘ 9-16 Mono-potassium phosphate, KH,PO,, 3 « 12:77 Di-potassium phosphate, KyHPO,, . 1-22 Potassium citrate, K.(CH;07), ‘ i 547 Di-magnesium phosphate, MgHPO,, 371° Magnesium citrate, Mgs(C.H5;0;)., 7 4°05 Di-calcium phosphate, CaHPO,, 742 Tri-caleium phosphate, Cas(PO4)», 8-90 Calcium citrate, Cag(CgH5;O07)o, . , % . 23°55 Lime combined with protein, ‘ 5:13 100-00 The mineral salts, as stated above, would amount to 0:90 per cent., as against 0°75 per cent. of ash obtained. According to Séldner 36 to 56 per cent. of the phosphoric acid and 53 to 72 per cent. of the lime are not in solution, but are in the colloidal form. The following shows the distribution of the phosphoric acid of the milk according to the author’s experiments :— P.U, as casein, combined with CaNa, . 0-0605 per cent. P.O; as Ca,(PO,)o, - 0-0625 P.O; as RgHPO,, . 0-077 35 P,0, as RH,PO,, ‘ , 0-020 Total P,O., ; 0-220 2 SUNDRY CONSTITUENTS. +1 The author’s conclusions differ from those of Soéldner, and are :-— (i.) One-third of the base with which casein is combined in milk is soda and not lime. (il.) Casein forms a molecular compound with calcium phos- phate. (il.) The citrates are dibasic, and not tribasic. Other Constituents of Milk.—Besides the constituents men- tioned, minute traces of silica, iodine, fluorine, acetates, and thio-cyanates have been described. None of the salts of milk require a detailed description. They, tovether with the acids and bases composing them, are described in any elementary book on chemistry. Among the other substances present in traces in milk the following have been described :—Urea, hypoxanthine and other nitrogenous basic substances, a colouring-matter, odorous sub- stances and alcohol (described by Béchamp, but certainly not ordinarily present). Lecithin, ©,,H,,O,PN, exists in small quantities in milk: on saponification 16 gives glyceryl phosphoric acid, fatty acids and choline ; it contains 3-84 per cent. of phosphorus, and vives 8:8 per cent. of P.O, on oxidation. The Gases of Milk.—lt is extremely probable that the vases of milk ave derived from the air by absorption during and alter milking. Oxygen, nitrogen (probably argon), and carbon dioxide are present in fresh milk. As the milk is kept the amount of oxveen decreases and that of the carbon dioxide increases; this is probably due to aérobie micro-organisms, which absorb the oxygen and give out carbon dioxide. The gases of milk may also include products of decomposition ; thus in decomposed milk, volatile sulphur compounds of evil odour are present. If such, as is probably the case in dirty surroundings, were present during milking they would be absorbed to some extent by the milk. The gases have no practical importance. Milk is sometimes charged with carbon dioxide under high pressure to form an effervescing drink. In this case, and in koumiss and kephir, products of fermentation of milk, the carbon dioxide is an important constituent. THe Far or MILK. Constitution.—The fat in milk is found in the shape of small elobules varying in size, according to Besana, Fleischmann, and other authorities, trom 0-01 mm. to 0-0016 mm. in diameter. There is some probability that the total weight of globules of any size is equal to the total weight of globules of any other size. 42 INTRODUCTORY—THE CONSTITUENTS OF MILK. The fat consists of a mixture of glycerides—7.e., ethereal salts of glycerol. It appears most probable that there are three acid radicles in combination with each glycerol residue, thus— C,H,0, C,H; CigH 3202 18**35 "2 which represents glyceryl butyro-oleo-stearate. This view has been formed from the following facts:—(1) Were the fat a mixture of glyceryl tributyrate with other glycerides, it would be possible to dissolve out the glyceryl tributyrate by means of alcohol, leaving nearly the whole of the other glycerides behind. This is not the case. The portion soluble in alcohol contains a notable quantity of the higher glycerides. (2) If glyceryl tributyrate existed as such in milk fat it should be possible to distil it off under reduced pressure, but this cannot be done. We know nothing of the way in which the fatty acids are combined with glycerol; it is convenient, however, to state the composition as if each glyceride existed separately. Composition.—The average composition of the fat of milk appears to be, from the mean results obtained by different observers, as follows :— Butyrin, 3°85 per cent. yielding 3°43 % Fatty acids and 1:17 % Glycerol. Caproin, 3°60, v4 aos si oe 0°86 ia Caprylin, 0°55 ,, 42 0°51 i se 0-10 i Caprin, 19 am i 177 nA i 0°31 a Laurin, 74 - os 6°94 4s ya 1:07 a Myristin, 20°2 ‘es ve 1914 $5 a. 253 e Palmitin, 25-7, DEMS 5 29) - Stearin, 1:8 3 of 1-72 ie $5 0°19 ‘a Olein, &c., 35°0 - » 33°60 - 3 3°39 re Total, 100-00 Insoluble, 87°65 Total, 12°53 Total, 94°84 C. A. Browne states that 1-0 per cent. of dioxystearic acid occurs in butter, and 0-1 per cent. of unsaponifiable matter. In this table, butyric, caproic, and caprylic acids have been classed as soluble in water, and the others insoluble ; this is not, strictly speaking, correct, as capric and, probably, laurie acids are also slightly soluble; on the other hand, caprylic acid pos- sesses so slight a solubility in water that it probably is not wholly dissolved. : The figure 87-65 per cent. is, however, a near approximation to the mean found for the insoluble fatty acids. The figure for the total amount of elycerol 12:53 also agrees with that found. FAT OF MILK. 43, Besides the constituents enumerated above, there also exist in the fat of milk traces of cholesterol (which doubtless replaces a portion of the glycerol), lecithin, a colouring-matter, and possibly also a hydrocarbon. Saponification.—On boiling with a solution of caustic alkali, the fat undergoes hydrolysis, thus— R *CyHs k, + 3NaOH = C3H,(OH)3 + NaR + Nak, + Nak, R, R, R, and R, representing radicles of the fatty acids. If the hydrolysis be carried out in presence of alcohol a portion of the caustic alkali is converted into an alkali ethoxide (alcoholate) thus— NaOH + C,H,OH = C,H,ONa + H,0. This acts in a slightly different manner fiom the hydroxide. though the ultimate products of hydrolysis are identical. The actions are probably as follows :-— ht *(.) 83NaOCLHs + CgHy ? 2, =C3H,(ONa)s + CH sR + CHR, + HGR. if “ (ii.) CgH;(ONa)g + BOH, = CgH,(OH)g + 3NaOH, (iii.) 3NaOH + C,H,R + CLH,L, + CHR, = 3C,H,;OH + NaR + Nak, + Nak, In the first stage, sodium ethoxide and fat form sodium glycer- oxide and ethyl salts (esters). In the second, the elyceroxide is decomposed by the water present into glycerol and sodium hydroxide: while, im the third, the esters are hydrolysed by the hydroxide into aleohol and sodium salts of the fatty acids (soaps). The action between the sodium hydroxide and the alcohol is never complete, and it is probable that the formation of esters is only partial: evidence of the formation of ethyl butyrate can be obtained by warming a little of the fat with alcoholic soda,. when the characteristic pine-apple odour of ethyl butyrate is at once developed. By carefully avoiding any excess of alkali and distilling the ethyl butyrate as soon as possible. Wanklyn and Fox have succeeded in obtaining about 3 per cent. of volatile acid (probably chiefly butyric) in the form of ester. It is probable that the equation (ii.) may not represent the way in which sodium glyceroxide acts on the substances present : a portion may follow this equation— liv.) C.HAONa), + 3C,H,OH = C.H,(OH), -+ 3C,H,ONa. * These reactions probably take place in stages. one acid radicle at a time being attacked. 44 INTRODUCTORY—THE CONSTITUENTS OF MILK. The glyceroxide may act on alcohol forming ethoxide, instead of on water forming hydroxide. Allen and Homfray have shown that by the action of a very small quantity of caustic soda on acetin (glyceryl tri-acetate), in the presence of alcohol, a very large proportion of ethyl acetate is formed, many molecules of ethyl acetate being produced by each molecule of sodium ethoxide; this can only be explained by the action shown in equation (1v.). Duffy has shown that ethyl and amyl stearate may be pro- duced from glyceryl stearate and sodium ethoxide and amoxide respectively. * The action of sodium ethoxide on milk fat has a practical bearing on butter analysis, owing to the volatility of ethyl buty- rate, which, unless precautions are taken, is liable to cause loss of butyric acid on saponification. From their sodium salts the acids may be set at liberty by the addition of a mineral acid. Properties.— Milk fat is insoluble in water, but dissolves about O-2 per cent. of this substance. It is not volatile, though when heated to 100° C. a loss of weight is noticed owing to the dis- solved water being volatilised. On further heating at this tem- perature, in a current of hydrogen, no change is noticed; but if oxygen be allowed access a gradual increase of weight, due to oxidation, is found; if the heating be prolonged, say for a week, the weight again decreases, and profound changes, the nature of which has not been elucidated, take place. Solid and Liquid Portions—The fat of milk being’ an undoubted mixture has no sharply defined melting point. If rapidly cooled to a low temperature it becomes solid, and melts on warming at from 29°5° to 33° C. By slow cooling it does not solidify as a whole, but behaves as a solution of fat of a high melting point in fat of a low melting point. The author obtained the following figures (Table II.) by allowing a sample to cool down gradually to about 25° C., and separating the liquid portion from the deposited solid :— TABLE I.—Properries or Mirx Far (Richmond). Original Fat. | Liquid Fat at 25° ¢. Solid Fat. Sp. gr. at 15°5°, cs 0 922 sa Reichert-Wollny, . 20°LGes 316 ce, 19°9 ee. wan Iodine absorption, . ss 2765 Original Fat. | Liquid Fat at 17° C. | Liquid Fat at 0°C. Reichert-Wollny, . 39:0 ec. 41:3 ce. 45-0 cc. PROPERTIES OF MILK FAT. 45, ie has also recorded the following experiments (Table TABLE III.—Properties o- Mik Far (P2221). | | | ' i iyi Liquid Liquid | Liquid i Liquid ' Liquid Solid at pe at 1-2? at 17-07| at 12-4 at 11-0, at 65° 26-29 Original: | ' Sp. gr. at 26-2’, | 0-908 | 0-912 0-916 | 0923 | ows oe ey Melting ci 36° site | ou Ae 44° Solidifying ,. 25° iiss oan ee ' F 35° Raishat €.c, 0. Cc : Gaee flexes G:C; eC ay hert- Oe AC: rie i Wollny, } 26°96 | 28°05 | 29°81 | es oF isa 0°36 | 32°34 | 34°10 19°91 Totjae a>sorP- |) 39-96 | 34-50 | 88: 50 | 40: 75! 42-75 | 52-25 | 58°50 25-28 | tion, Solid Fat Solid Fat Solid Fat Solid Fat Solid Fat deposited deposited deposited deposited dleposited from Liquid] from Liquid | from Liquid | from Liquid from Liquid ab 26:2? by | at 212° by | at 170° by | at lea by atl by cooling to cooling to cooling to cooling to cooling to 21 2e. Wo. Let, 10, feo Melting point, 435 31° IS? 7 los eae ’ i Solidifying ,, re 165 18 I? SF" Revellwy, VI 2013 et, | 2759 ee, | wwF0 ee. | QUAF ow, Biwt oe.’ oor aig ea 138-70. | dbs 45-50 Sud5 The above figures all show that the liquid fat is somewhat richer in both volatile and unsaturated acids than the original fat, while the solid portion is correspondingly poorer in these constituents. There is. however. no sharp seperation The density of the fat of milk is as follows Temperature. Mean. Limits. | Authorities. pial pts ania reeag, : | = | 09307 (solid) os | Fleischmann. ane | 0°9118 (liquid) | 0-9094—0-9140 ee aes ee 0-9113( ,, ) | O-9104—-0-9117 . Author. | — (in glass) O's667(,, -) | 08850 —O°s635 ) Numerous. The last Genet is not a true density, as it is not corrected for 46 INTRODUCTORY—THE CONSTITUENTS OF MILK. the expansion of glass between 155° and 100°; it has been assumed that the volume of the glass instrument used to deter- mine the density is the same at 100° as at 15°5°. The error has no practical importance when the figures thus obtained from different samples are compared, as they are all subject to the same correction. From the average specific gravities given above the author has calculated the true specific gravities and specific volumes ; these are— Temperature Specific Gravity. Specific Volume. | Calculation. { 4 { 15° | 1 -e 09300 10753 1:0844 78° | ae 0:9057 11041 | 11041 395° 4°" 09045 1:1056 | 11056 100° os 08637 | 1:1578 1:1578 The figures calculated are based on the assumption that the expansion is regular between 15° and 100°, and that it averages 0-000863 for each degree Centigrade; on this assumption the specific volume of liquid fat at 15° is higher, and the specific gravity 1s lower than that of the solid. 15°5° ; inS? (calculated) is 0°922. It is interesting to note that the specific gravity of the liquid fat obtained by the author (above) had a specific vravity of 0-922. The specific gravities of the liquid fats obtained by Pizzi appear to have been taken at the temperature at which the fat was separated, and on calculating to 15° have values from 0-921 to 0°925,. On the whole the evidence available appears to show that the specific gravity of solid fat is greater than that of liquid fat at the same temperature. In connection with this, it may be mentioned that E. W. T. Jones has shown that the specific gravity of other fats is greater when partially solidfied at 37°8° than when liquid at this tem- perature. The index of refraction of the fat of milk averages 1°4566 at 35°, and the limits observed have been 1:4550 to 1-4586, Stohmann has determined the heat of combustion of butter fat as 9-231 calories per gramme, while Atwater found from The specific gravity of liquid fat at PRODUCTS OF HYDROLYsIZ. 47 9-320 to 9-362 calories in three samples of butter, which appear from the analytical results of Schweinitz and Emery to have been of doubtful purity. The fat of milk is soluble in all hydrocarbons which are liquid at the ordinary temperature, in their halogen derivatives, in ether, carbon bisulphide, nitro-benzene, and acetone. It is slightly soluble in alcohol and to a considerable extent in amyl alcohol when cold, but in all proportions when hot. Glycerol, when hot, dissolves it to a very small extent. It appears to mix in all proportions with esters. Fatty acids have a limited solvent effect, those of higher molecular weight dissolving more than the lower homologues. Phenol also dissolves it to some extent. On cooling a strong solution of the fat in any solvent, the portion deposited has not the same composition as the original fat, but is of the same nature as the solid portion obtained by slow cooling of the melted fat. The molecular weight of the fat has been determined by Carelli and Carcano by Raoult’s cryoscopic method in benzene solution to be from 696 to 716. That calculated from the amount of alkah necessary for saponification is 720 to 740, Propucts oF HypROLysis. Glycerol.—This is the simplest tri-hydric alcohol and has CH,OH | the constitution— CHOH. It was discovered by Scheele in | CH,OH 1779 in olive oil, and was first recognised in butter im 1784. The anhydrous product is a thick syrupy liquid, which can be obtained in crystals by cooling to a low temperature; the melting point of the solid glycerol is given as 17° C. by Henniger and 20° C. by Nitsche. It boils at 290° C. under the ordinary pressure, but undergoes slight decomposition ; it can be readily distilled without change under reduced pressure. It is not volatile with steam. .An aqueous solution containing less than 75 per cent. glycerol can be boiled without loss; but from solu- tions containing more than 75 per cent. glycerol it Is somewhat volatile (Hehner). Anhydrous glycerol volatilises slowly at 100° C',. When heated above 150° C. it is inflammable. 55° 155° same temperature is 1-4748. : ; When heated to its boiling point, especially if not pure, various is 12675; the refractive index at the The density at 48 INTRODUCTORY—THE CONSTITUENTS OF MILK. products, of which acrolein (C.H,O) is the most important, are given off. Di- and tri-glyceric alcohols are also formed. By the action of acid oxidising agents—e.g., chromic acid and potassium permanganate in acid solution—it is wholly converted into carbon dioxide and water. Alkaline permanganate converts it quantitatively into oxalic acid. By the action of bromine in the cold glycerose is formed, which is an aldehyde; by further oxidation with bromine at a high temperature, or by boiling with CH,OH | dilute nitric acid, glyceric acid CHOH is produced. | COOH COOH | ; ; nea Tartronic acid CHOH is. under certain conditions, also | COOH produced together with glycolic, glyoxylic. oxalic, and formic acids. Glyceric acid appears to have a constitution similar to lactic acid (q.v.), from which it differs only by containing the group CH.(OH) in place of CH,. It forms a lactone and a dehydro- derivative, and contains an asymmetric carbon atom. By the action of fuming nitric acid (mixed with sulphuric acid to preserve its strength) glyceryl tri-nitrate (nitro-glycerine), usually mixed, with small quantities of di- and mono-nitrates, is formed. This is a heavy explosive liquid of specific gravity 1-6 and of bmited solubility in water. This compound is best known as a powerful explosive. With strong sulphuric and phosphoric acids glyceryl mono- hydrogen sulphate and mono-glyceryl di-hydrogen phosphate are produced. These have the composition— $0,(OH)OC3H;(OH), and PO(OH),OC,H;(OH), respectively. When glycerol is heated with alkalies above 250° C. a variety of products are formed ; among these are formic, acetic, acrylic, and lactic acids. The oxygen of the air seems to play an impor- tant part in these changes, as all the products contain more oxygen and less hydrogen. No change takes place below 250°, especially in the absence of air. Several glyceroxides are known—i.e., bodies in which the hydrogen of the hydroxyl groups is replaced by metals. By heating lead oxide with glycerol, lead glyceroxide is formed. Glycerol also dissolves lead oxide. ; GLYCEROL, 49 By treating glycerol with sodium dissolved in alcohol a crys- talline deposit of the composition C,H-NaO,, C,H,O is formed, which, when heated at 100° in a current of hydrogen, loses alcohol. It is a white amorphous powder, very hygroscopic and immediately decomposed by water. Calcium, strontium, and barium hydroxides are freely soluble in glycerol, and form glyceroxides, which may be dissolved in water; the aqueous solutions do not give precipitates with carbonic anhydride. By the action of hydrochloric and hydrobromic acids, mono- and dichlor-hydrin and mono- and dibrom-hydrin are produced. There are two possible mono-chlor- and mono-brom-hydrins : thus— CH,Cl CH,(OH) CHOH and CHCl CH,(OH) CH,(OH) and similarly two di-hydrins: thus— CH,Cl CHCl CH(OH) and CHCl CH,Cl CH,(OH) Both compounds are simultaneously produced. By the action of alkalies on both the dichlor-hydrins, epichlor- CH,Cl hydrin CH is produced. ydrin CH 0 is produ A mono-iod-hydrin also appears to be produced hy the action of hydriodic acid. The penta-chloride and penta-bromide of phosphorus produce trichlor- and tribrom-hydrins, which are the «-§-y-trichlor- and a-8-y-tribrom-derivatives of propane. Phosphorus tri-iodide or concentrated hydriodic acid produce a mixture of allyl and iso-propyl iodides with propylene. By the action of dehydrating agents acrolein, acrylic aldehyde, C,H,O is formed. Glycerol is very soluble in water and alcohol, but insoluble in ether and chloroform. Cholesterol, C.,,H,,OH, is a mono-hydric alcohol, containing one unsaturated bond. This is shown by its combination with two atoms of bromine to form dibrom-cholesterol, C.,,H,,Br,0H. unchanged. It is levo-rotatory, having an [¢], — 36°6 (Drag- endorff) or — 31°6 (Lindenmeycr). Re It is easily soluble in hot alcohol, crystallising out on cooling in characteristic plates; occasionally from alcohol and more often from ether it is obtained in needles. Cholesteryl acetate, melting point 92°, is obtained by the action of acetic anhydride on cholesterol. The benzoate is obtained by { 50 INTRODUCTORY—THE CONSTITUENTS OF MILK. heating cholesterol with benzoic acid under pressure, and melts at 150° to 151° C. The most characteristic reaction is the following, due to Sal- kowski:—About 10 milligrammes of cholesterol are dissolved in 2 c.c. of chloroform, and the solution shaken with an equal measure of strong sulphuric acid in a corked test tube. The chloroform layer becomes blood-red, passing to cherry-red and purple, the last colour being permanent for several days. The sulphuric acid acquires a well-marked green fluorescence. If the test tube be not corked, or if the chloroform solution be poured into a basin, the colour changes to blue, green, and, finally, yellow, probably due to moisture. On addition of water the solution becomes paler, then blue, and, finally, nearly colourless, while showing a fine green fluorescence. By cautiously heating cholesterol with a drop of strong nitric acid and adding ammonia before the product has cooled com- pletely, a yellowish-red coloration is produced. If a mixture of 3 measures of concentrated hydrochloric acid and 1 of a solution of ferric chloride be evaporated with a little cholesterol, a reddish-violet coloration changing to blue is pro- duced. By substituting sulphuric acid for hydrochloric acid, a carmine colour is produced, passing gradually to violet, which is changed to scarlet on treatment with ammonia. Fatty Acids. Acids of the Series, C,,H2,4;COOH.—As far as is known, only the normal acids of this series, in which n is an odd number, occur in the fat of milk. Butyrie Acid, CH,CH,CH,COOH.—Grunzweig has proved that the butyric acid of the fat of milk is normal. This acid is a liquid with a characteristic smell, which is specially developed in dilute solution; the anhydrous acid has a sharp acid smell, the characteristic smell being hardly perceptible. The acid solidifies at —19° C. The solidified acid melts at —2° to +2° C. according to Linnemann, and at —4:5° to —2° C. according to Zander. The boiling point is variously stated according to different authorities. Thus— Linnemann gives . ; , i 3° Lieben and Rossi, ‘i F 163" . Kahlbaum, . z ‘ ‘ 161°5° Brubl, si ‘ j : 161°5°-162°5° Zander, 2 i ‘ 3 ‘ 162°3° The author finds . . 4 P F = 161°5°-162°5° 20° The density is given as 0-9587 at ro by Bruhl, 0-9746 at 0° by Zander, and 0:9886 at 0° by Linnemann. FATTY ACIDS. 51 It is very difficult to prepare the anhydrous acid by distillation alone, the last traces of water being retained with great obstinacy ; dehydrating agents remove this water, and the acid is somewhat hygroscopic. It is soluble in all proportions in water, but is separated as an oily layer on saturating the solution with calcium chloride. It is extracted from aqueous solution by ether. From dilute solutions it distils 2-1 times as fast as water—z.e., the vapour arising from a dilute solution contains 2-1 times the proportion of butyric acid contained in the solution. Its solu- bility in the mixture of higher fatty acids of milk fat is very small. By the action of strong chromic acid at the boiling point it is oxidised to a mixture of carbon dioxide and water, but dilute solutions are unaffected. Alkaline permanganate oxidises it to carbon dioxide ; Johnstone states that oxalic acid is formed from butyric acid by the action of alkaline permanganate, but other observers are unanimous in denying this. The salts of butyric acid are all soluble in water. When ignited they leave a residue of the carbonate of the metal (except the silver and mercury salts, which leave metallic silver and no residue, respectively). The calcium salt has the following solubility :— 100 parts of water at 0° C. dissolve 19°4 parts. 20° 7 o ” “ ” Vi ” 3 5, 60°-85° a 150, as » —:100° 3 15°38, A cold saturated solution is precipitated by heat. It crystal- lises in rhombic needles from cold solutions, and in rhombic prisms from hot solutions. The barium salt is much used for determining the molecular weight of the acid; it cannot be dried at 100° C. without slight loss of butyric acid, but is quite permanent at 90° C. One thousand parts of absolute alcohol dissolve 11:7 parts at 30° and 2°45 parts at 14° according to Luck, who has used this method of separating it from barium formate, acetate, etc. Silver butyrate crystallises by cooling a hot solution in needles, but by spontaneous evaporation in monoclinic prisms. 100 parts of water at 16° dissolve 0°413 part. Both the acid and calcium salt form molecular compounds with calcium chloride. Butyric acid occurs in the free state in perspiration and as ethyl salt in the oils of Heraclewm giganteum and H. spondylium, hexyl butyrate being also present in the latter; the oi from the seeds of the parsnip (Pastinaca sativa) consists chiefly of octyl 52 INTRODUCTORY—THE CONSTITUENTS OF MILK. butyrate. Ethyl butyrate is a volatile liquid of a smell recalling the odour of pine apples. Caproic Acid, CH;.CH,.CH,.CH;.CH,COOH.—Keefoed has proved that the caproic acid of the fat of milk is normal. This acid is an oily liquid with an unpleasant goat-like smell. It boils at 205° C., solidifies at —18° C., and melts at —1°5°. Its. density at 0° is 0°9446 according to Zander. It hardly mixes with water, is extracted by ether from an aqueous solution, and possesses considerable solubility in the mixed higher fatty acids of milk fat. From a dilute aqueous solution it distils four times as fast as water. The calcium salt differs from calcium butyrate by increasing in solubility on heating; 100 parts of water dissolve at 11° to 12° 2°36 parts, at 17°5° 2°58 parts, and at 185° 2°71 parts of calcium caproate. It crystallises in needles. The barium salt dissolves in 100 parts of water to the extent of 12 parts at 11° to 12°, and the solubility decreases on heating. Caprylic Acid, C,H,,COOH.—This acid crystallises in plates or needles melting at 165° C., and boils at about 236° C. It has a faint unpleasant odour of sweat, and a sharp rancid taste ; it is difficultly soluble even in hot water, from which it crystal- lises in plates. From dilute solutions it distils eight times as fast as water. Barium caprylate crystallises in anhydrous plates, and is soluble to the extent of 6 parts in 100 parts of water at 20° C. The calcium salt crystallises in long thin needles, and is less soluble than the barium salt—0‘6 part per 100. Caprice Acid, C,H,,COOH.—This acid has a faint goat-like odour, and is only very slightly soluble in water. It crystallises in brilliant plates, melting at 30° C.; it boils at 268° to 270°. The barium and calcium salts are nearly insoluble in water, even on boiling, and the salts of the alkalies are the only ones appreciably soluble. Laurie Acid, C,,H,,COOH.—The acid is solid at ordinary temperatures, and is not soluble to any extent in water; it passes over to a very appreciable extent when distilled with steam. It crystallises from alcohol in needles, melting at 43°6° C. It cannot be distilled without decomposition at the atmospheric pressure, but at 100 mm. it has a boiling point of 225° C. The salts of the alkali metals yielded by the acids previously described are soluble in strong salt solution; the laurates of sodium and potassium are, however, precipitated by strong sodium chloride solutions, but not by weaker ones. Lauric acid is a leading constituent of cocoa-nut and palm-nut oils. Myristic Acid, C,;H,-COOH.—This acid crystallises in laminee melting at 53-8° C. and boils at 250-5° under 100 mm. FATTY ACIDS. 53 pressure ; it cannot be distilled alone. The acid is insoluble oe and its salts of the alkali metals are precipitated by salt. _ Palmitie Acid, C,;H,,COOH.—The acid is quite insoluble in water; it crystallises from alcohol in tufts of finely crystal- lised needles ; and the melted acid solidifies on cooling to a pearly crystalline mass. The melting point is 62° C., and it boils under 100 mm. pressure at 271°5° C.; it cannot be distilled under atmospheric pressure without decomposition. According to Hehner and Mitchell a saturated solution of palmitic acid in alcohol of specific gravity 0°8183 contains from 1:32 to 1:03 grammes per 100 c.c. at 0° GC. 100 parts of absolute alcohol at 19-5° dissolve 9-32 parts; it is, how- ever, readily soluble in boiling alcohol and crystallises out on cooling. Stearic Acid, C,.H,,COOH.—This acid is quite insoluble in water; it crystallises from alcohol in white, nacreous lamine, melting at 69°2° (Heintz) or 68:°5° (Hehkner and Mitchell) to a colourless liquid, which on cooling solidifies to a crystalline whitish mass. Under 100 mm. pressure it boils at 201° C. It cannot be distilled under the atmospheric pressure without decomposition. Hehner and Mitchell have shown that at 0° (. a saturated solution in alcohol of 0-8183 specific gravity contains from 0-142 to 0:158 gramme per 100 c.c. Absolute alcohol dissolves about 2°5 grammes per 100 c.c. The salts of stearic acid are, with the exception of those of the alkali metals (soaps), insoluble in water and almost insoluble in alcohol. The salts of palmitic acid resemble them very much. The most marked difference between these two acids is the difference of solubility of the magnesium salt; that of stearic acid is practically insoluble in cold alcohol, while that of palmitic acid possesses a slight, but appreciable, solubility ; the presence of magnesium palmitate causes, however, appreciable solubility of magnesium stearate. All salts of stearic acid (and palmitic acid) are partly decom- posed by water into basic and acid salts; the salts of the alkali metals (soaps) cannot be dissolved without becoming appre- ciably alkaline. They are, however, soluble in hot alcohol without decomposition, forming solutions which gelatinise on cooling. . Soaps of stearic and palmitic acids are quite insoluble in 12 per cent. solution of sodium chloride. General Properties of Acids of the Series, Cy Hen+1.COOH. —The following table (IV.) gives a summary of the leading pro- perties of these acids :— 54 INTRODUCTORY—THE CONSTITUENTS OF MILK. TABLE IV.—PRopertizs oF THE ACIDS OF SERIES Caren + ,COOH. solubility of | Distilla catenin | Poe wa |e Sp. Gr. pep. | are. | Gacum salt.) tow” Water=1, I | Butyric, 88 | 0-9746 at 0° 162° 9? 17-6 at 20° F 21 Caproic, | 116 |0-9446 at 0° | 205° | —1-5° | 27 at185) 4 Caprylic,) 144 | 0-9270 at 0° 236° = -16-5° 0-6 at 20° 8 Capric, | 172 | 0-893 at 30° 269° 30° 0-1 at 20 ? at 100 mm. Lauric, | 200 | 0-875 at 43-6°| 225° 43-6° 0-039 at 15°, ? Myristic,| 228 | 0-8622 at 53-8° | 250-5° 53-8° insoluble : Palmitic | 256 | 0-8527 at 62° 271-5° 62° rs 68-5° Stearic, | 284 | 0-8454 at 71° 291° to is | 69-2° At 0. Viscosity. | | Solubility in | gojnbilityin Alcohol] D Ee y s yne per sq.cm. Acid. | Water. Sp. Gr. 0°8183. at 20°. | Butyric, . . | all proportions | all proportions 01634 Caproic, ‘ soluble se 03263 Caprylic, . . | 0°25 °/, at 100° 3 05860 Capric, » jor mS very soluble te Lauric, é very slight 5 Myristic, . gs. Yl insoluble soluble Palmitic. <5 12 )*)., Stearic, | 35 0°15 °/, None of the acids of this series absorb iodine or bromine, as they are saturated compounds, and are not appreciably attacked by strong sulphuric acid or fused alkalies; the lead, copper, and zinc salts of the lower members of the series (up to lauric) are soluble in ether, but lead, copper, and zinc myristate, palmitate, and stearate are not very soluble in this menstruum. Acids of the Series, C,, Hs», - ;COOH—Oleic Acid, C,-H,.. COOH, —This acid is probably a constituent of butter; it is extra- ordinarily difficult to prepare it in the state of purity, as it is altered by exposure to the air, and no well-defined stable com- pound is known. It is extremely doubtful whether it has ever been isolated ; the formula given for the acid is to some extent a matter of conjecture, as there is great probability that the analyses from which it was deduced were made on impure OLEIC ACID. 55 products. For the same reason there is some doubt as to its properties. The following properties are assigned to oleic acid :—A colour- less liquid free from smell, which moistens the skin, solidifies at 4° C., and melts at 14° C. Specific gravity at 14° C. 0-898, and at 100° C. 0-876. It cannot be distilled under atmospheric pressure, but boils under 100 mm. pressure at 286° C. It can be easily distilled below 270° in a current of superheated steam. Oleic acid is insoluble in water, but very soluble in alcohol even if considerably diluted. To a solution of 1 c.c. of oleic acid in 95 per cent. alcohol 2-2 ¢.c. of a mixture of equal parts of acetic acid and water can be added without causing precipitation ; further quantities, however, throw the oleic acid out of solution. On exposure to the air it turns yellowish, and becomes rancid ; it then reddens blue litmus paper, while pure oleic acid is said not to do so. By the oxidation of oleic acid dioxystearic acid is formed. By the action of bromine di-brom-stearic acid is formed: this is'a heavy yellow oil, which has not been crystallised. By reduction with zinc and hydrochloric acid oleic acid is ayain formed. Oleic acid also absorbs iodine from Hubl’s reagent, and is said to form chlor-iodo-stearic acid. Strong sulphuric acid acts on oleic acid, forming stearo-sul- phonic acid or sulpho-stearic acid; on boiling with water, sul- phuric acid is split off and hydroxystearic acid is formed, with other products. When oxidised by alkaline potassium permanganate di-oxy- stearic acid is formed. The salts of oleic acid behave with water in much the same way as the salts of stearic and palmitic acids. All the oleates are soluble in alcchol, and those of copper, lead, and zinc are soluble in ether. By the action of fused alkalies oleic acid is split up into salts of acetic and palmitic acids. Nitrous fumes act on oleic acid in a characteristic manner ; the liquid oleic acid is transformed into the isometric solid elaidic acid melting at £5° and boiling at 288° C. at 100 mm. pressure. Baruch has proposed the following formule for oleic and elaidic acids :— Oleic Acid. Elaidic Acid. CgH,;,—C—H cael i ll H—C—(CH,);—COOH COOH—(CH,);—C—H Acids of the Series. (',H»,-3;COOH — Linolie Acid, C,-H,,COOH.—It is not known whether this acid exists nor- mally in butter fat; if so, the proportion is probably not large. 56 INTRODUCTORY—THE CONSTITUENTS OF MILK. It, however, is present in many vegetable oils, and will thus be a constituent of margarine. Linolic acid is an oily substance of slight yellow colour, having a faint acid reaction; it dissolves readily in alcohol and ether. It remains fluid at low temperatures. The salts of linolic acid resemble those of oleic acid, but are more soluble in alcohol and ether. Nitrous acid does not produce a solid acid. Both the acid and its salts readily absorb oxygen from the air, and form resinous substances. Linolic acid absorbs 4 atoms of bromine, forming tetra-brom+ stearic acid, which is a crystalline substance melting at 114° to 115°; from this linolic acid can be prepared by reduction with zinc in a solution of hydrochloric acid in alcohol. Acids of the Series, C,,H:,,_;COOH—Linolenie Acid.— This occurs in vegetable oils. It is a liquid, even at very low temperatures, and has a fishy odour. It forms a hexa-brom- compound melting at 177° C. Comparison of the Acids of the four Series.—The following table (V.) will show the main differences between stearic, oleic, linolic, and linolenic acids, the corresponding members of the four series:— TABLE V.—Comparison OF THE Four Typical Fatry AcIpDs. . ae Melting Bromine Meltin, Behaviour with Acid. Condit:on. Point. Compound. | Pont, Nitrous Acid. Stearic, Solid 68°5° None sje No action Oleic, Liquid 14 2 Br. Liquid | Solid elaidic acid Linolic, 93 Below-18° 4 Br, | 114°—115° Liquid product Linolenic, es Very low 6 Br. | 177° | Fe 3 Acia Behaviour with Eroduct foumed Meltin: o a ali ng " wae Sulphuric Acid. ee: Point. Character of Eroduct: Stearic, No action No character- : ; : istic product Oleic, Sulphonic Dihydroxy- 134° | Insoluble in cold acid formed | stearic acid water. Very little ee : ; soluble in ether. Linolic, Great action | Sativic acid 172° | Soluble in hot water. Insoluble : , Seite in ether. Linolenic, ss 9 Linusic acid 204° | More soluble in hot water than sativic acid. In- soluble in ether. RANCIDITY. 57 Rancidity—Products of Decomposition.—But little is known of the real nature of the changes which take place when butter becomes rancid. The following statement will give an idea of the probable nature of the changes :— The first action seems to be hydrolysis of the fat, splitting it up into fatty acids and glycerol; the latter, perhaps, is not liberated as such, but is oxidised, yielding aldehydes and acids soluble in water, but not so volatile as the soluble acids of butter ; the volatile acids are liberated, and the smell of these can be detected in rancid butter. The odoriferous principle is destroyed. The unsaturated fatty acids are oxidised to form hydroxy acids, which are perhaps slightly soluble in water, but not volatile ; the total capacity for combining with bromine is reduced by this cause. It is probable that the fatty acids of the series, C,,Hz,,.,;COOH, are but slightly affected. The effect of rancidity is— (1) To diminish the glycerol produced on saponification, (2) To increase the soluble acids. (3) To increase slightly the volatile acids. (4) To decrease the insoluble acids, (5) To increase the total setae Eeopeeon of acids. (6) To greatly increase the free acids. (7) To deeninich the unsaturated acids by (8) The formation of hydroxy acids. If the change takes place in the presence of water, some of the products are soluble therein ; hence the fat separated from the water will not have the same characters as fat which has become rancid alone. If freely exposed to the air, some of the products may be volatile. 58 ANALYSIS OF MILK. CHAPTER II. ANALYSIS OF MILK. Contents.—Specific Gravity of Milk—Estimation of Total Solids—of Ash—of Citric Acid—of Milk-Sugar—of Cane-Sugar—of Starch—of Fat and Cream—of Proteins—of Total Acidity—Analysis of Milk Products. The Specific Gravity of Milk—-Modes of Expression.— Specific gravity is the weight of a unit of volume. The unit of volume is a cubic centimetre, the unit of weight one gramme, and the specific gravity of any substance is the weight of one cubic centimetre in grammes. As one cubic centimetre of water at 4° C. weighs one gramme, the specific gravity of water at 4° C. is exactly 1; at temperatures higher and lower than 4° C. water expands, and therefore has a specific gravity less than 1. Table VI. gives the specific gravity of water at different tem- peratures :— TABLE VI.—Speciric Graviry or WATER. Temperature. Specific Gravity. | Temperature. | Specific Gravity. oc. 0:99988 40° 0°99236 4° 1:00000 50° 0°98817 10° 0-99974 60° 0°98334 15°55° (60° I.) 0°99908 70° 0-97789 20° 099827 80° 0-97190 30° 0:99577 90° 096549 37°78° (LOU F.) 0°99313 100° 0°95856 As at 4° C. one cubic centimetre of water weighs one gramme, a practical method of ascertaining the specific gravity at this temperature is to take the weight of any volume of the liquid and to compare it with the weight of an equal bulk of water. To ascertain the specific gravity at any other temperature—say, for example, 30° C.—the weight of any volume of liquid is ascer- tained and compared with the weight of water at that temperature SPECIFIC GRAVITY. 59 divided by the specific gravity at that temperature—in the case taken 0-99577. The following formula may be used for determining specific gravity :— wt. of a known vol. of liquid x sp. gr. of water at same temp. Sp. gr. = P. BF wt. of same volume of water at same temperature. In practice it is customary to assume that water at 15°55° C. (60° F.) has the specific gravity 1. Thus, to ascertain the specific gravity at 15-55° C. (60° F.) it is customary to weigh a known volume of liquid, and to compare it with the weight of an equal volume of water at that temperature. All specific gravities in this volume are stated in this way unless otherwise mentioned. In order to avoid confusion the symbol ° specific gravity at ae is often used to express this mode of expression. This means that the weight of a volume of liquid at 15:55° is compared with the weight of an equal volume of water at 15-55°. a ; 3 : 1533" BOL Similarly, the expression specific gravity at —je> «OF yo 38 used to express the true specific gravities at 15°55) and 20° respectively. It is occasionally convenient to compare the weizht of a liquid at some other temperature with the weight of water at the same temperature ; thus the specific gravity of fats is taken sometimes ‘ : ‘ Low, at 100° C., and the expression specific gravity at P55; 1s used to express the value obtained by dividing the weight of a volume of fat at 100° C. by the weight of an equal volume of water at 100° C. If we ascertain the weight of water held by a certain vessel at a definite- temperature, we can ascertain the specific gravity of any liquid by filling it with the liquid at the same temperature and weighing it. If we fill the vessel with the liquid at any other temperature, the volume contained will not be the same as that of the water, owing to the expansion of the vessel itself altering the capacity. Nevertheless, specific gravity is frequently ascertained on the assumption that the vessel does not alter in capacity by change of temperature. As the vessel is usually made of glass, this mode of expression of specific gravity may be . : 20° a termed the “apparent specific gravity in glass at poe (or whatever the temperature may be). ; As a matter of fact, specific gravities of milk are usually 60 ANALYSIS OF MILK. o ' : ae ae determined as ‘“‘ apparent specific gravities nm glass at BBB 2 Determination of Specific Gravity.—There are two methods of determining specific gravity, which is, as above stated, the weight of unit volume, or, expressed as an equation— W 5 = rz We may either determine the weight of a known volume, or the volume of a known weight. Both methods are used in practice, the first in two ways :— (1) A vessel of known volume is filled with the liquid and its weight taken. (2) A plummet of known volume is immersed completely in the liquid, and the loss of weight due to the displacement of an equal volume of liquid noted. The second method is applied (3) by immersing a float of Fig. 2.—Sprengel Tube. known weight, and noting the volume immersed; the volume immersed will be equal to a volume of the liquid of weight equal to that of the float. Determinations of specific gravity by method (1) are made by specific gravity bottles and Sprengel tubes, by method (2) by a Westphal balance, and by method (3) by hydrometers, of see lactometers are special forms of limited range suited for milk. For exact determinations of the specific gravity of milk, a Sprengel tube (Fig. 2) presents many advantages. It is a U- shaped tube with narrow capillary ends bent outwards at right angles, one being rather smaller than the other; the wider of the two has a fine line etched round it, to which the liquid in the tube may be adjusted, the U and the other capillary being completely filled. The weight of the dry and empty tube is first ascertained, the tube is then filled with pure distilled water, and immersed in water at exactly 15:°55° C. (60° F.); when it is seen that no SPECIFIC GRAVITY. 61 further expansion or contraction takes place, the water should be adjusted to the line on the wider capillary by the cautious appli- cation of a piece of blotting-paper to the end of the narrow capillary ; the tube is then wiped dry and weighed. The differ- ence in the two weights gives the weight of the water contained in it. The tube is then filled with milk and immersed in water at 15°55° C. (60° F.), and the milk similarly adjusted to the line ; the weight of milk divided by the weight of water gives the 15°55° 15°55" A specific gravity bottle is used in a similar manner ; the liquid, after inserting the stopper and immersing the bottle in water at 15-55°, is adjusted to the line by drawing out the excess with a very fine tube. A Sprengel tube of 10 to 20 c.c. capacity is the most suitable size; it is a disadvantage to use a larger one, as the time taken for the milk to assume the temperature of the surrounding water is so much increased that there is danger of a portion of the cream separating. The advantages of a Sprengel tube over a specific gravity bottle are :— specific gravity of the milk at (1) Greater surface for a given volume; and therefore the temperature is adjusted quicker. (2) There is no stopper to fit; consequently, no error can be due to difference of position owing to inaccuracy of fit. The Westphal balance (Fig. 3) consists of a balance of the steel-yard”’ type, carrying a glass plummet at one end; it is so adjusted that the pointer is at zero when the plummet hangs in air, and is provided with a weight, which, when hooked on to the end, causes the pointer to be at zero when the plummet is immersed in water at 15°55° C. The beam is divided into ten parts, each indicated by a notch, and riders weighing the same, yp tbo and yooo Of the weight are provided. — . a To take the specific gravity, the plummet is immersed in milk at 15:55°, and riders are placed on the notches of the beam till the pointer is at zero. If the ,', rider is on notch 3, the specific eravity is 1-03; if, in addition, the ;35 rider has to be placed on notch 2. the specific gravity is 1032; and if, in addition, the yolga Tider has to be placed on notch 4 the specific gravity 1s 1-u324. If a rider is already on a notch, and it is desired to place another thereon, it may be hung on the turned up end of the rider already in position. ’ A rule may be given as follows :—Count 1 for the weight hung on the end, the first decimal from the notch on which the 1 rider is hung. the second decimal from the notch on which $2 ANALYSIS OF MILK. the J, rider is hung, the third decimal from the zi, rider, and the fourth decimal from the yqyp Tider. This method has the advantage of being somewhat more rapid than the use of the Sprengel tube, but is not quite so accurate, as the adjustment of riders and balance cannot practically be performed with very great accuracy. In dairy work the lactometer is generally used. From a strictly scientific point of view, there are many objections to lactometers, but their practical convenience is so great that they are instruments of extreme value. | | \ Fig. 3.—Westphal Balance. i The faults of lactometers are :—(1) They do not indicate true specific gravities, but the inverse of this—specific volumes ; consequently, the scale is not divided into equal parts. The divergence from equality is, however, so small in a lactometer which has only a limited range, as to render it practically admissible to treat the smaller divisions as equal. . (2) The exact point at which the level of the liquid cuts the stem of the lactometer cannot be ascertained, as, owing to surface energy, the liquid is attracted to a higher level round the stem of the lactometer than the surface of the liquid; moreover, the height to which the liquid is attracted varies with the nature VARIATIONS OF SPECIFIC GRAVITY IN MILK. 63 of the liquid. As milk has always the same composition within narrow limits, there is no practical difference in the height to which it is attracted round the stem; the eye soon becomes trained in making the proper allowance for this. (3) Lactometers are only correct at the temperature at which they are graduated ; at other temperatures their volume varies : no inconvenience on this account is felt in practice, as this is allowed for in the tables given for correcting the specific gravity to a temperature of 15°55° C. (60° F.). Practical instructions for the use of lactometers will be civen later under the “ Testing of Milk.” : Variation in Milk.—The specific gravity at 15°55° C. (60° F.) of the milk of individual cows varies from 1:0135 to 1:0397; when the mixed miik of a herd is tested it rarely falls outside the limits of 1-030 and 1034. The average specific gravity of milk is 1:0322. The specific gravity is dependent on two causes—the amount of solids not fat, which, being dissolved in water, raises the specific gravity; and the fat, which, being lighter than water, lowers it. By removing the fat (with a small proportion of other constituents) as cream the specific gravity of the milk is raised. By the addition of water the specific gravity is lowered. The specific gravity has been—and is—largely used as a test for the addition of water to milk ; for the detection of large amounts of water to milk it has some value. That it is a test of the roughest kind is shown by the following facts :— (1) The variations in specific gravity are from 1:0135 to 1:0397—7.e., nearly twice its bulk of water could be added to milk of the highest specific gravity to reduce it to the lowest. These, of course, are exceptional cases, and the specific gravity of the mixed milk of a herd is nearly always between 1:030 and 1:034. At least 10 per cent. of water could be added to milk of 1-034 specific gravity before it would be suspected by this test. (2) A milk of 1:032 specific gravity, if the cream is all removed, would give a product of about 1-036 specific gravity; and an addition of rather more than 10 per cent. of water would bring the specific gravity back to 1-032. (3) If to milk of 1:032 specific gravity sufficient cream be added to raise the percentage of fat 4 per cent., the specific gravity will be found to be about 1:028. The same result would be arrived at were the milk allowed to stand, and the upper portion removed. As an absolute test the specific gravity is able to be greatly misleading; as a preliminary test it is of the greatest import- ance, and should never be neglected. As stated above, the specific gravity is raised by the solids 64 ANALYSIS OF MILK. not fat, and lowered by the fat. This fact is not only true quali- tatively, but also, as the following demonstration will show, quantitatively. By our definition that specific gravity (S) is the weight (W) of the unit volume (V), we get the equation— W Soap a Ro See 2) Let us suppose we have a mixture (having the specific gravity 8) of two substances, A and B, of differing specific gravities S, and Sz. Let us suppose that the respective weights are A and B, and Then by (1) 2 Volume of ea volume of B= ce and volume of mixture —100 Sy Ss, S¢ Then 100 A(S,-S,) 100 inp tet (fe Now in the same way 8,-8 8=8,+B8(3t :) 100d, /" As both 8, and 8, are constants, we may write 8 =Sa+ BS x Kp ‘ ed @ = Be AS x Ka Kg and Ky being constants . . (2) Now, as A + B = 100, A is the percentage by weight of this substance ; and as 100 x S expresses the total number of grammes in 100 c.c. of the mixture, AS is the number of grammes of this substance in 100 c.c. From the equations above given we can deduce the law that ‘if two substances of differing specific gravity be mixed, the specific gravity of the mixture will be equal to the specific gravity DERIVATION OF FORMULZ. 65 of one of the substances plus the number of grammes of the other per 100 c.c. of the mixture multiplied by a constant factor.” Regarding milk as a mixture of fat and a solution of solids not fat in water, we can say that the specific gravity of a milk is equal to the specific gravity of the solution of solids not fat plus the number of grammes of fat per 100 c.c. multiplied by a constant. In the solution of solids not fat we have in 100 c.c. of it x grammes of solids not fat; let us assume that their density is y. Then xz grammes will occupy a volume 7 - Let the specific gravity of the solution be S. The 100 ¢.c. weigh 100 S grammes, and the water in this weighs 100 S — x grammes; it also measures 100 -- a c.c. Now, as the specific gravity of water is I, 100 N= 2 = 100 ~~ y 100 S=100 +2 - = y Seiew! : = (3) 1UU y y—1. ; i Now, toa is a constant, provided that y remains constant. 4 Putting the equation into words we find ** that the specific gravity of a solution of solids not fat is equal to 1 plus the number of grammes of solids not fat in 100 ¢.c. multiplied by a constant.” It is known, however, that the specific gravity of substances in solution is not quite constant, but varies slightly with dilution. The following figures will show that in milk the law just enu- merated holds good within the limits of experimental error. .\ poor skim milk was diluted with water, and the total solids and specific gravity at 15-55° estimated :— i} Total Solids per Cent. Specifle Gravity. Constant. i i ' a Wo. ¢ serv ae | gs Lost | 0008688 8-748 1 03343 | 0003693 SBIS 103170 = | ~~ O-003694 777 Lo2930 | 0003684 | T4536 102829 | ~—-0-003690 6-455 1-02439 | 9-003688 ) | From the laws expressed by equations (2) and (3) we see that the specific gravity of an aqueous liquid containing a substance in solution or in admixture can be expressed equally as a direct 5 66 ANALYSIS OF MILK. multiple of the number of grammes per 100 c.c. ; for if we suppose that the substance A is water, Sa will equal 1, and equation (2) can then be written— S=1+BS x Kp. which is practically equation (3). Formule for Calculations.—In order to deduce a formula expressing the relation between specific gravity and percentage by weight of fat and solids not fat, let us call the specific gravity (for convenience) 1+58, the percentage by weight of fat F, and of solids not fat N. ; Then the number of grammes of fat per 100 c.c. will be F x (1 +8) and of solids not fat N x (1 +8). The weight of the water in 100 ¢.c. is then 100 x (1+8)- Nx (1+8)-F x (1 +58) grammes ; and its volume 100 x (1+8)-Nx(1+8)-F x (1+8) ce. The volume of fat and solids not fat in 100 cc. is therefore 100 — (100 x (1 +8) - Nx «(l1+8)-F «(1 +8)) ce which equals Nx(l+8)+Fx(1+8)-1008 . (4) Let us assume that the specific gravity of fit is f and of solids not fat n. F x (1 +8) Then the volume of fat in 100 cc. is - and of solids N x (148) 7 not fat 3 therefore Nx (1+8)+F x (1 +8)-1008="2048) , Nx0+8) n or 100S=Nx(1+8)- a ar fel ) 1 Gea Now, as » and / are constant, we may write for C = "), a; and for (>). b. ‘ Then the equation stands 100 8 THR TON+OF ae em. BY or 100S=Nx(1+8) It is usual, however, to estimate total solids (T) and fat in an analysis. T=N+F, and, therefore, N=T-F, DERIVATION OF FORMULE. 67 The equation (5) may be written 100 8 Leyte (D-F+oF 100 ON re T+@-a)F a (6) _ In expressing the specific gravity of milk it is usual to do se in lactometer degrees, which are the specific gravity multiplied by 1,000 minus 1,000. Thus if the specific gravity be 1-032, the lactometer degrees are 1-032 x 1,000 — 1,000 = 32. Let us express lactometer degrees by the symbol G. Then G = 1,000 §, and, substituting this in (6), we get The specific gravity was expressed as 1 + S for ease in caleu lation ; it is better, however, to substitute the symbol D in the formula, which then stands as $= l0a T+ 10 (b- a) F J (t bo a or oy haat a (eee ; Cone Ce)? ae ome n—l /-1 As, by the definition above, a = ear and b = ——, we could calculate a formula, did we know the specific gravities of solids not fat and fat, but we do not know both of these. Fleishmann has determined the specific gravity of the fat of milk to be 15° C, 09307 at joes gravity of solids not fat in solution. Moreover, Fleischmann’s determination of the specific gravity was made on fat in the solid state, and it is possible that in milk it may have a different specific gravity. By transforming equation (7) into the form po By ef Pee F ~ 10a ° TD ( a )x a and making a large number of determinations of 4 T, and F but it is impossible to determine the specific in different milks, we can form each pair of results into simul- taneous equations and solve them. In this way we can get a large number of values for a and b, and, from the mean of these, we can calculate the specific gravities of fat and solids not fat respectively. This method is not wholly free from objection, 68 ANALYSIS OF MILK. as, unless there is a considerable difference between the figures actually determined, the figures from which a and 6 are calcu- lated are so small as to be greatly affected by experimental. error; while, if the difference be large (as in the case of analyses of cream and skim milk), it is found that the experimental error is also increased. For this reason, and also for the reason that the specific gravity of fat and solids not fat are themselves hable to slight variations, it is necessary to deduce the formula from a great many determinations, which means much labour in calculating. In order to ascertain the specific gravities of fat and solids not fat in milk, the author has calculated their value from over 200 analyses made by the most exact methods at his command, and finds the following figures :— Specific gravity of fat, : ‘ ; 0-93 solids not fat, . . 1616 ” ” It is seen that the author’s figure, calculated from actual analyses, agrees with Fleischmann’s determination of the specific gravity of fat. As the specific gravity of milk does not vary much, it will not make an appreciable error if, instead oft, the expression 10399 be used; this form of calculation is much easier. The idea of deducting a relation between specific gravity, fat, and total solids appears to have arisen with Behrend and Morgen, who published a table. Shortly afterwards Clauznitzer and Mayer, and Hehner published formule, but as they were founded on inaccurate data, they are now abandoned. Fleischmann and Morgen next published a formula in which the specific gravity of fat was assumed to be 0-94; this was corrected by Fleischmann after his determination of the specific gravity of fat as 0-93. His formula is eis 0-2665-4 +125, Hehner and the author deduced the formula T = 0-254 G + 1-164 F.* This ig in the less scientifically correct, but more convenient. form ; as it was found that milk differing appreciably in specific gravity from 1:0322 did not give results which agreed well with the formula, various approximations have been made to this. The author has calculated a formula which gives practically * In the original paper a slight correction for skim milks was included in the formula; this has now been abandoned. MILK SCALE. the same results, but is more scientifically cor- rect, and which does not require the application of approximations. This is T = 0-262 H + 117 F. As the previous formule were deduced from analyses to which objection could be taken, the author has deduced a new formula from the results of analyses made as exactly as possible. 4 G T = 0-2625 Le2h ds j25 D + This has heen found to : expressed by the simpler formula T = 7] SF -- Ol4 within very small limits if. the mete gravity lies between 1-020 and 1-036, ( ) a he formula T = za +; F also approximates closely to that of Hehner and the author. Other formule have been devised by J. C. Brown, Babcock, Leonard, and others. Of the above formule, that of Fleischmann agrees best with the results when Noxhlet’s method of fat estimation is used ; that of Hehner and the author when the Society of Public Analysts’ methods are employed; while if the methods mentioned later as most exact in the author's opinion be employed, the author's formula sives the most satisfactory results. The fat calculated from the specific gravity and total solids almost invariably agrees within 0-2 per cent. with the determination made by the appropriate method. Milk Scale.—In order to save calculation the author has devised a slide rule, known as the “milk scale’? (Fie. 4), from which the percentage of fat can be read off directly from the specific gravity and percentage of total solids. On one side a scale is placed indicating total solids, 1 per cent. of total solids being represented by 1 inch: on the other side the fat is shown by a scale of 1-2 (1! inches) to 1 per cent.; the slide carries the specific gravity scale. 1) being equal to O25 (4) inch. The line indicating the specific om Qo SPECIFIC CRAVITY \2 Trt Re Es Far gv a TT THOTT Be ve TOTTI tite 12 rorac_ J) sovios 10 wy a LACTOMETER READING B84IRD & TATLOCK LONDONL'S ll if poo o i ¥F 13 4 T NE we & Te Titi i 16 Li AO i TUMPEHATUSC W = Fig. 4. Milk Scale. | 69 70 ANALYSIS OF MILK. gravity found is placed against the total solids estimated; an arrow placed 0°14 (4) inch from the end of the specific gravity scale then gives the fat as calculated by the formula. T=025G+412F 49-14. To facilitate reading, Cassal and Gerrans propose to add two sliding pointers, one on the total solids scale, and one on the specific gravity slide, which are first placed against the part of the scales corresponding to total solids and specific gravity found respectively, and the two pointers are then adjusted. This arrangement prevents the possibility of error in adjusting the slide. The author has also employed a runner made out of a piece of brass bent round the milk scale, in which two holes are cut, leaving a narrow bar between them; this bar partially covers both the total solid and specific gravity scales, and has a fine line drawn upon it at right angles to the scales. By adjusting this line to the total solids, and the specific gravity to the line, the object sought by Cassaland Gerrans is attained. Stokes uses a strip of transparent celluloid on which a fine lineisdrawn. The idea of the runner is due to Lieutenant Mannheim of the French Artillery, who, in 1851, devised it for a logarithmic slide rule. The scales are divided into tenths, hundredths being estimated by the eye; a decimal scale, or, better, a vernier, as suggested by Sykes, can be applied to the runner, rendering it easier to read the second place of decimals. This, however, is not neces- sary, the error due to unavoidable circumstances being greater than the error of computation of the hundredths. Tables are given from which the fat calculated from different percentages of total solids and specific gravities can be read off. By our definitions (p. 58) get ae n a and from the values given above in the formula mentioned, a and 6 can be calculated. Thus, taking the formula T = 0°2625 £ +12 F, l fc 02623 - je ee a-b 625 Tn and 125 OF Sc a = 0°38] and b= 0°U762 ; | 1 now Sa 5 Picea SOR oy P c= | and Ba ae and, therefore, n= 1-616 specific gravity of solids not fat, and J=0950 ,, S fat. SPECIFIC VOLUME. 7/1 From the mode of deducing equation (7) we see that a is the number of grammes that the weight of 100 c.c. of milk is greater than the weight of 100 c.c. of water, when 1 gramme per 100 c.c. of solids not fat is contained therein; the density being, by definition, the weight of 1 c.c d —~ are respectively the a * 700 “8° T00 difference in specific gravity due to 1 gramme per 100 c.c. of solids not fat and fat. It is also apparent that we may calculate from any analysis the amount that 1 gramme of total solids per 100 c.c. has raised the specific gravity, and, from this, the specific gravity of the total solids. Thus, using the same symbols as before G =a x 2, and t=a4 (t here representing the specific gravity of the total solids). Thus, if a milk has a specific gravity of 1032 and contains 12 per cent. of total solids, 32 1 12) = 032 x 0x and z= 0:2584 and t= 1348. It is occasionally useful to calculate the specific gravity of the total solids of a milk, as the total solids of skimmed milk have a considerably higher specific gravity than those of whole milk. Specific Volume.— By our definition of specific gravity, we write S = ,.; we may also write, = Ds or, in words ee a ea . ote ee | aa ; & expresses the volume of 1 gramme; this is called specific volume. The expression & is, therefore, a mode of indicating D specific volumes ; as G (degrees of specific gravity) is 1,000 times the specific gravity minus 1,000, so, (degrees of specific volume) p | is 1,000 ménus 1,000 times the specific volume. In Table VII. the values of degrees of specific volume for each half degree of specific gravity from 20 to 36 are given. It is seen from the formule above, that 1 per cent. by weight lowers the specific volume to the same extent as 1 gramme per 100 ¢.c. raises the specific gravity—v.e., specific volume, not specific gravity, varies directly as percentage by weight. 72 ANALYSIS OF MILK. TABLE VII.—Spsciric Graviry anD VoLuUME oF MILK. i Degrees of Deerces of Degrees of Degrees of Specific Gravity. Specific Volume. Specitic Gravity. Specific Volume. 20-0 19°6 28:0 27:2 20°5 201 28°5 27°7 21°0 20°6 29°0 28°2 21:5 21:0 i 20 5 23°7 22-0 215 : 30°0 29°'1 22-5 a) 30°5 29'6 23-0 22°5 31:0 30:1 23°5 23°0 315 30°5 ' 24-0 23-4 32-0 31-0 | 24:5 23°9 32°5 315 25-0 24°4 33°0 31-9 25°5 24-9 335 32-4 26:0 254 34:0 32:9 265 25°8 B45 83-4 27-0 26°3 35-0 33°'8 27°5 26°8 35 5 34:3 36-0 34°7 Mode of Averaging Specific Gravities—It is not, there- fore, correct in averaging milk analyses, where specific gravities and percentages by weight are expressed, to obtain the average specific gravity by adding the specific gravities together and dividing by the total number, but specific gravities must be first calculated to specific volumes, and these averaged, and the average specific gravity deduced from the average specific volume. Thus, to average the following analyses :— Specific gravity, . . 1°022 Total solids, * - 20°0 58 5 1-036 3 10°0 9) The average total solids is soa = 15; but the average 1-022 + 1-036 1 2 0-9785 + 09653 1 age = far = 1-0289. The error is, however, small if the specific gravities do not differ greatly, and may very frequently be neglected. On the other hand, if, instead of averaging percentages of total solids by weight, we average the number of grammes per 100 c.c., we obtain correct results by averaging the specific gravities. The following rules may be stated :— specific gravity is not = 1:029, but FORMULA. 73 (1) If equal volumes of different milks be mixed, the specific gravity of the mixture will be the mean of the specific gravities of the milks. (2) If equal weights of different milks be mixed, the specific volume of the mixture will be the mean of the specific volumes of the milks. Instead of taking the solids not fat as one substance, we may consider its constituents—lactose, protein, and mineral matter —separately. Calling the percentage of fat F, lactose L, protein P, and mineral matter A, we may write : = lob F + 10¢c L + 10d P + We A by the same reasoning employed in deducing formula (4). The author has deduced from the mean of many analyses the formula G __ O71 FR +4L4 25714 P 4 840A. From these factors the following specific vravities are deduced, as previously shown :— Specific gravity of fat, F O03 oe o lactose, 1-606 ve a protein, 1-346 - i mineral matter, oS Using these specitic eravities, together with Vieth’s estimate of the proportions of lactose, protein, and mineral matter— 13:9: 2—we can calculate what the specific gravity of solids not fat should be. As Victh’s proportions are by weight, we must transform specific eravities to specific volumes. 1 eee ee = = 0. Specitic volume of lactose Ley o drotein = — U-743 » pote “ieay = a es mineral matter = =-_ = 0-182. 2a) Then specific gravity of r 1 . SS oan at aes ee eS res 2 ete G1 “UP. = 13 0G $9 X O73 +2 X Os? ~ VOLES = YO 2 which agrees with that given above, 1-616. It is a useful check on an analysis to calculate the specitic gravity from the percentage of milk-sugar, protein, fat, and 74 ANALYSIS OF MILK. mineral matter; this should agree within small limits with that found. The Alteration of Specific Gravity by Change of Temperature.—Milk, like all other substances, alters in specific gravity by change of temperature. Though it contains a large amount of water, it does not share the anomaly which this substance possesses of attaining its maximum specific gravity at 4° C. (39° F.). It decreases in specific gravity when heated from its freezing point — 0°55° C. (31° F.). The following figures (Table VIII.) show the average apparent expansion of milk in glass -— TABLE VIIIJ.—Expanston or Mik. i 1 | empen inte in | Volume. q ba ae in Volume. | 31 1-00000 60 | 1-00229 35 100016 65 100298 40 100041 70 1:00372 45 1:00074 75 10045] 50 100114 f 80 100549 55 1:00164 | | b | The expansion is greater with rich milk than with poor milk ; the above figures referring to milk having a specific gravity of 1-032 and containing 3°8 per cent. fat. Table CXXXI. in the Appendix affords a means of correcting to 60° F. the specific gravity of milk when taken by a lactometer at any temperature from 33° F. to 85° F. The table gives specific gravities from 1-020 (20 degrees) to 1-036 (36 degrees) and is applicable to whole milk only. The portion from 45° F. to 75° F. is, with a few alterations, due to Vieth; this has been repeatedly checked by the author, and in a few places slightly changed in accordance with the results obtained. The other portion has. been calculated by the author. The table is used by looking up the degrees of specific gravity found (or the nearest whole degree) in a horizontal line, and the temperature in a vertical line; the figure at the intersection of the two lines is the specific gravity corrected to 60° F. The specific gravity of separated milk may be corrected to 60° F. by the following table. As the expansion is practically uniform for the variations in quality met with, the table is given in a simpler form. RECKNAGEL § PHENOMENON. 1D TABLE IX.—For Correctine Speciric GRavIty of SEPARATED MiLK To 60° F, Temp. Take off. Temp. Add on. | Temp. Add on. | °F, ie OF °F, 50 11 60 0-0 70 14 51 10 61 01 71 16 52 0-9 62 0:3 72 18 53 0's 63 0-4 eo 19 54 O-7 64 0 74 2°0 dad 0°5 65 06 7) 2-2 56 O-+ 66 0'8 | 76 2:3 57 0:3 67 0-9 17 Qt 58 U2 68 11 | 78 26 59 Ol | 69 1:2 79 Oy The author has devised a scale for correcting the specific gravity of milk to 60° F. It is usually engraved on the “ milk- scale,’ and is used by adjusting the specific gravity found (on the slide) to the arrow at 60° F. The corrected specific gravity is found opposite the temperature at which the determination was made. The corrected specific gravities obtained by the ‘‘ milk-scale ” agree generally within 0-1 of those taken from the table. At very low temperatures, howéver, there is sometimes a larger difference. 8. H. Collins has devised a milk scale in which the temperature correction for specific gravity is automatically made; the points denoting temperature and specific gravity observed are brought together, and on the other side of the scale the percentage of solids not fat corresponding to any percentage of fat is read off. The Rise of Specific Gravity of Milk on Standing.— Milk drawn from the udder contains a large number of air bubbles, and its specific gravity cannot be taken; after the expiration of an hour or so these have disappeared, and a specific gravity determination is possible. It was first observed by Recknagel that the specific gravity taken after the expiration of one hour was lower than the specific gravity subsequently obtained. He found the rise in specific gravity to be regular, more rapid at low temperatures than high ones, and to amount on the average to 0-001. He attributed the change to an alteration in the volume of the casein. Vieth completely confirmed Recknagel’s observation, and found the average rise to be 0°0013; Bourcart also observed the phenomenon. The author has studied Recknayel’s phenomenon (as this ‘ 76 ANALYSIS OF MILK. change in specific gravity has been called). In about 70 per cent. of his experiments the rise in specific gravity has been observed, varying from 0-0015 to 0-0003, and averaging 0-0006, while in 30 per cent. of the observations no rise in specific gravity was indicated. The experiences of Babcock and Farrington agree with that of the author. The author’s experiments have confirmed the statement of Recknagel, that the rise is more rapid when the temperature is low than when high ; the same ultimate specific gravity is attained whatever the temperature. Recknagel’s phenomenon appears to be unconnected with the milk-sugar, and Recknagel’s explanation is not the correct one. It is difficult to reconcile the idea that it is enzymic, with the fact that the rise is more rapid at low than high temperatures. The author’s experiments on the change of density and specific heat of cream by heating made in conjunction with 8. O. Rich- mond have shown that Recknagel’s phenomenon is due largely to the increase of density of the fat on solidification. Contrary to the author’s former conjecture, there seem to be no particular periods of the year in which Recknagel’s pheno- menon is observed or not. Samples have been found at all seasons which show a marked change in specific gravity, while others examined almost simultaneously have shown no change. It must be mentioned that Recknagel’s phenomenon has been denied by some. Smetham attributes the change in specific gravity solely to the presence of air bubbles. The weight of evidence is, however, greatly against this view; it is incon- ceivable that air bubbles generated by milking a cow should be persistent for twelve hours, while if they are formed in the milk by other means, say by running through a separator, they dis- appear in one hour. The final specific gravity is always taken as the true specific gravity of milk, and the term is so used in this volume. The Estimation of Total Solids.—The total solids of milk are estimated by evaporating the water and weighing the residue. Wanklyn’s Method.—Wanklyn proposed to limit the time of drying to three hours at the temperature of boiling water ; he weighed 5 grammes in a platinum basin, kept it for three hours on a briskly boiling water-bath, and, after cooling in a desiccator, weighed the residue. This method has now entirely fallen into disuse, as the residue thus obtained still contained a quantity of water, which could be driven off by further evaporation. Method of Society of Public Analysts.—A very obvious modification of this is to continue the drying on a water-bath or TOTAL SOLIDs. TV in an oven at 100° C. till the weight is constant. This method has been adopted by the Society of Public Analysts. It is not, however, possible to attain absolute constancy, as a decomposition due to heating takes place, and the weight continually slightly diminishes on further heating; for this reason the weight is usually considered constant when less than 1 milligramme per hour is lost on further drying. The method gives very good results, and duplicates agree closely ; but it is doubtful whether the results represent accurately the true total solids of the milk. First, an absolutely constant weight is not attained; and, next, the residue is markedly brown, indicating decomposition; the point taken as constancy is really a point where it may be assumed that the bulk of the water is driven off, and comparatively little decomposition has taken place. The author has found by taking smaller quantities of milk —about | gramme—and spreading this over a large surface during evaporation, that a nearly white residue is obtained, and constancy of weight can be attained. It appears probable that the decomposition to which the browning is due takes place during the heating of the milk before evaporation is concluded. In support of this view it may be noted that Cazeneuve and Haddon have observed that formic acid is produced by heating milk to the temperature of boiling water, and Johnstone has found that formic acid added to milk had an enormous influence on the results. The results obtained by the estimation of total solids by the evaporation of 1 gramme spread over a large sur- face, from which the water was very quickly driven off, were always slightly higher than when 5 grammes were used, when evaporation was very much slower, In order to secure rapid evaporation, the milk has been spread over a large surface by the use of sea sand and other granular substances. Vieth has found that evaporation on sand gives practically the same results as direct evaporation im a basin. Babcock’s Method.—Babcock has used asbestos as a medium for spreading the milk over. The method as adopted by the Association of Official Agricultural Analysts (of America) is described elsewhere. The author has found Babcock’s method most satisfactory, and finds it convenient to operate as follows :— Place about 3 grammes of fine asbestos fibres in a small platinum basin, and ignite strongly (preferably in a muffle). The asbestos should be soaked in hydrochloric acid, and thoroughly washed before use; when ignited and shaken with water containing a few drops of phenolphthalein no red colour should be produced. After weighing, add about 5 grammes of milk, and again weigh as quickly as possible to the nearest milligramme. Place the basin 78 ANALYSIS OF MILK. for an hour or two on a water-bath, and dry in a water-oven till constant in weight. The residue thus obtained shows no signs of browning, and a constant weight, which shows no appreciable change on pro- longed drying,. can be obtained. The “total solids” by this method are somewhat hygroscopic, and care must be exercised in weighing. Macfarlane’s Method.—Macfarlane uses “chrysotile” or Canadian asbestos for this purpose; this substance cannot be ignited, being a hydrated mineral, and on treatment with water affords a very sensible amount of soluble alkali; this causes a loss of weight owing to its action on the milk, and for this reason chrysotile is not so satisfactory as the Italian asbestos. The residue obtained by drying on “chrysotile ’’ is very distinctly brown, and the results are much lower than those given by other methods. Adams’ Method.—Adams uses a paper coil, which is first dried at 100° C. and weighed, for the estimation of total solids. The results thus obtained are frequently low, owing probably to the presence of alkaline salts. Duclaux has proposed the use of sponge, and Ganntner of wood fibre; but these substances have never come into general use. Drying.—The author has found that by evaporation zn vacuo over sulphuric acid good results are obtained if the milk be spread on blotting-paper or on asbestos; the result is slightly higher than when the drying is performed at 100° C. In order to shorten the time of drying, Gerber and Raden- hausen experimented with acetic acid and alcohol. They found that by coagulating the casein with these substances a skin no longer formed on heating, and the time of evaporation was materially shortened. For this reason the use of acetic acid, or alcohol, or a mixture of the two, has been largely adopted for the estimation of total solids. A much greater browning of the total solids takes place, and constant results are quite impossible of attainment when acetic acid or alcohol is used; by a some- what close adherence to arbitrary conditions as to time of drying very fair results may, however, be obtained in this way in a short time, but the method cannot be recommended where accuracy is of importance. Revis proposes the use of acetone. It may sometimes be of importance to estimate the water driven off, instead of deducing it from the difference between the percentage of total solids and 100. To accomplish this, about 4 grammes of asbestos should be placed in a U-tube, and, after drying by passing a current of dry air, this should be weighed. About 5 grammes of milk should be weighed in, and the U-tube DRYING APPARATUS. 79 suspended in a beaker of water. This is connected with another weighed U-tube filled with pumice moistened with strong sul- sphuric acid, and provided with a bulb in which the bulk of the water can condense. A current of air (or preferably, hydrogen) dried by sulphuric acid should be passed through the tubes, and the water in the beaker boiled. After about three hours’ heating, the sulphuric acid tube should be removed, and, after cooling, weighed. The increase of weight of the sulphuric acid tube will give the weight of the water in the milk taken. It is not advisable to dry the total solids at temperatures exceeding 100° C., as the decomposition of the residue by heat is increased at higher temperatures. Drying Apparatus.—For the drying of total solids the following conditions may be laid down for the drying apparatus :— (1) The temperature must not exceed 100° C. (212° F.). (2) The moisture must be removed as goon as it is converted into vapour. The usual form of water-oven used consists of a water-jacketed metal box with a door to it; very little provision is made for the removal of the moisture, as no current of air is allowed to circulate through the whole of the interior. Various forms of air-baths, with a reyulator for maintaining a constant temperature of 100° C. (212° I), have been proposed ; of these, the best are those of Griffin and Adams. These do not vive quite satisfactory results for milk analysis, because the temperature for which they are regulated is the temperature of the air in the bath, while the basins in which the milk is dried are heated to a somewhat higher temperature by conduction, The following figures were obtained with a Griflin’s air-bath ; a porcelain capsule filled with mercury was placed on various shelves in the bath, and the temperature of the mercury noted. The air had a constant temperature of LUQ> C. :— Temperature on bottom, — . 156° Pn on cork on bottom, 1u2- a on shelf, . : : log? 4 in upper part, - ’ 96° Constancy of temperature cannot be depended upon in an air- bath; it is, therefore, preferable to use a water-oven. The author has devised a water-oven for milk analysis, which has given highly satisfactory results. It consists of a jacketed copper box, opening only at the top, and closed with a movable lid; on the lid is a chimney about 1 foot high. The bottom portion of the jacket contains four 8-foot coils of thin copper tubing, which communicate with the exterior by four holes at the side of the bath, and with the interior 80 ANALYSIS OF MILK. by four holes, one in each corner. The jacket is closed, except: for one opening, in which a condenser is placed. About 1 inch from the bottom a sheet of copper is fixed, in which is a round hole of diameter equal to half the width of the interior. The jacket is filled with distilled water, which is heated either by a steam coil or a gas flame; perforated copper shelves are used to support the basins, etc., containing the substances to be Infet For Steam. - Condenser, D> Qa ay) Sa — eg 9) / a \, A ) FE if i y rh OL) Y Z Oi LA \ fn V4 aS au) 4 Meee ALLARD YY [PONTO ALUMI SELL ALU LOU PLLL Y a’ ee = Air. Fig. 5.—Diagrammatic View of Air-bath. dried. The heating is chiefly done by conduction from the sides of the bath through the shelves; a current of hot air, approach- ing in temperature to that of boiling water, is always passing through the bath, and rapidly removes the vapour. The condenser is supplied with cold water, and prevents loss of water. It conduces greatly to the efficiency of the bath to use distilled water, as no scale is produced on the coils and sides ESTIMATION OF ASH. 81 of the oven. To prevent loss of heat the oven may be lagged with felt, asbestos, or kieselguhr. The most efficient condenser has been found to be a spiral coil of tubing (preferably copper), which fits rather closely into a tube. The cold water enters at the top, and passes by a straight portion of the tubing to the lowest coil, whence it circulates upwards, and finds an exit at the top. A diagrammatic figure of the bath will assist comprehension of the details (Fig. 5). A very convenient water-bath for milk analysis is that devised hy Vieth: the chief advantage of this lies in the lid, which, instead of merely having holes made in it in which the basins fit, has a copper ring fastened into each. This enables the basins to be taken off without contact between the fingers and the hot lid. This bath may be heated by a steam coil or a vas flame, and is conveniently supplied with water by a constant level apparatus. If dry steam is available it is very convenient to use steam coils to heat the bath, and to condense the steam after it has passed the coils. The condensed steam can be used us distilled water, and is usually pure enough for all purposes. It is liable, however, to contain traces of copper, if this metal is em- ployed in the construction of the coils, condenser, etc.: if the boilers prime to any extent, it will also contain impurities (salts, scale-preventing composition, etc.), derived from the boiler. Estimation of Ash.—The residue of total solids serves excel- lently for the determination of the ash. By igniting over a small Bunsen flame, or an Areand burner, or ina muffle, a white ash can be obtamed. The temperature must not be allowed to rise above a barely perceptikle red heat. or distinct volatilisa- tion of alkaline chlorides may occur. Hf the asbestos method of total solid estimation has been used, a somewhat higher tem- perature may be employed than if simple evaporation in platinum has been resorted to A more exact determination is obtained by evaporating a larger quantity of milk than is usually taken for total solid esti- mation—-25 to 50 erammes—and gently igniting till thoroughly charred: the mass is extracted with hot water and filtered, the insoluble portion and the filter being (after washing) ignited at ured heat till white; this will give the insoluble ash. By evaporating the filtrate and cautiously igniting at a low temperature, the soluble ash is obtained. The sum of the soluble and insoluble ash gives the total ash; the results obtained in this way are usually shehtly higher (about 0°02 per cent.) than the ash obtained by ignition of the total solid residue. 6 82 ANALYSIS OF MILK. If it be desired to examine the ash further, it is desirable to keep the insoluble ash separate from the soluble portion. In the solution of the soluble ash the alkalinity may be deter- 3 cae, _ N.. , mined by titration with i6 acid, methyl orange being used as an indicator; -and the chlorine, by titration with standard nitrate of silver, using potassium chromate as indicator. The insoluble ash is dissolved in a slight excess of dilute hydro- chlovie acid, and the solution (nearly neutralised with ammonia, if necessary) heated to boiling; a cold saturated solution of ammonium oxalate is dropped in slowly till the addition of a further drop gives no more precipitate. After standing at least two hours the precipitate is filtered off, washed, and ignited at a low temperature to convert the oxalate into carbonate; it is best to moisten the ignited precipitate with ammonium carbonate solution and re-ignite at a very low temperature. The pre- cipitate, after weighing, is dissolved in dilute hydrochloric acid, keeping the bulk small; ammonia is added to alkaline reaction, and the small precipitate of calcium phosphate collected, ignited, and weighed. Its weight is subtracted from the previous weight, and the difference gives the weight of the calcium carbonate, which, multiplied by 0-4, gives the calcium, or by 0°56 the lime, contained in it; the weight of the calcium phosphate multiplied by 0°3871 gives the calcium, or by 0°5419 the lime, contained in it. The total calcium or lime is the sum of the two. The filtrate is made strongly ammoniacal by the addition of ~ 0880 ammonia and allowed to stand twenty-four hours. The precipitated magnesium-ammonium phosphate is filtered off, washed with dilute ammonia, ignited, and the magnesium pyro- phosphate weighed. Its weight multipled by 021622 will give the magnesium, and by 0°36036 the magnesia contained in it. To the filtrate from this, magnesia mixture is added. The precipitate of magnesium-ammonium phosphate is filtered off after twenty-four hours and treated as above. From the total weight of the two quantities of magnesium pyro- phosphate the phosphoric anhydride is calculated by multiplying by 0°63964 ; to this is added the phosphoric anhydride in the calcium phosphate calculated by multiplying the weight by 0°4581. The above method has proved satisfactory in the author’s hands, though it takes no account of the traces of iron present, which is precipitated with the calcium phosphate, or the mag- nesium-ammonium phosphate. If desired, this may be estimated by dissolving up the precipitate of calcium phosphate and the first magnesium-ammonium phosphate precipitate in dilute hydro- chloric acid, and determining the iron colorimetrically as sulphide, ferrocyanide, or thio-cyanate. ESTIMATION OF MINERAL CONSTITUENTS. 83 To estimate alkalies, another portion of milk is ignited, as hefore, and the total ash dissolved in dilute hydrochloric acid and boiled ; a few drops of barium chloride solution are added containing not more than (1 gramme of barium to 100 grammes of milk, and the boiling ton tinmed for some minutes. After some hours the precipitate of barium sulphate is filtered off, ignited, and weighed ; its weight multiplied by 0°34335 will give the sulphuric anhydride in the milk. If an excess of barium chloride has been added, a little phosphoric acid, or ammonium phosphate. may now be dropped into the filtrate, though it is not necessary if the quantity of barium chloride given above has heen employed. .\ quantity of ferric chloride solution sufficient to colour the solution brown is added, and the filtrate made alkaline with ammonia, The precipitate is well washed, and the filtrate evaporated and very cautiously ignited ; the weight will vive the alkaline chlorides. The residue is dissolved in water, and the solution should be quite clear; if it is not so, a httle ammonium carbonate is added, the liquid evaporated to dryness, and the residue cautiously ienited : the residue is again taken up with water, the solution filtered and os vaporated, and the residue « cautiously wnited and weighed, The chlorine in this may be titrated by standard silver nitrate, using potassium chromate as indicator. The potassium and sodium are calculated by the following formula :— Let W = weight of alkaline chlorides and C = weight of chlorine therein. The weight of sodium =~. 2-997 14254 W. rr ve ‘potassium = 24254 W - 3-997 C. The potassium may be direetly estimated by evaporating the solution of alkaline chlorides with an excess of platinum tetra- chloride solution almost to dryness; the pasty residue is treated with 80 per cent. aleohol containing about 5 per cent. of ether, and washed repeatedly with this: the alcohol is passed through a weighed filter or, preferably, a Gooch crucible, and the preci- pitate is finally transferred to this and washed with ether. It is then dried at 100° C. and weighed: the weight multiplied by 03056 will give the potassium chloride: this subtracted from the weight of the alkaline chlorides will give the sodium chloride. The potassium chloride multiplied by 05244 will give potassium and by 06314 potash. The sodium chloride multiplied by 0°3932 will give sodium and by 05299 soda. The above scheme of analysis has been worked out so as to use as little milk as possible, as the amount available is some- times limited. Many obvious modifications are available and will readily suygest themselves to analysts: thus the chlorine 84 ANALYSIS OF MILK, may be gravimetrically estimated, and, if the amount of milk be sufficient, the phosphoric acid may he separated from another portion by the molybdie acid method. Such modifications will be found in works on inorganic analysis, and need not be described in detail. If boric acid be present, it will be found to interfere with the results of the analysis, as a portion of this remains in the insoluble ash: this may be removed by evaporating the acid solution to dryness and repeatedly evaporating with small por- tions of methyl alcohol. It will also interfere with the estimation of alkalinity in the soluble ash, as the alkali shown by methyt orange will be due to borax; the chlorine is best estimated in this case gravimetrically as silver chloride. Boric acid is detected by slightly acidifying the ash with hydrochloric acid and dipping a piece of turmeric paper into the solution ; on drying, this will assume a pinkish-brown color- ation, turned a very dark green—almost black—on moistening | with a solution of sodium bicarbonate. Cribb and Arnaud pre- pare turmeric paper by boiling 2 grammes of turmeric and 2 grammes of tartaric acid with 80 per cent. alcohol till the latter is dissolved, and soaking strips of filter paper in this solution. It is very delicate, and should be kept in the dark. Another test is to moisten the ash with dilute sulphuric acid and add strong alcohol; if boric acid be present, the alcohol will burn with a greenish flame on applying a match. Boric acid may also be detected in the milk direct, by acidi- fying with hydrochloric acid, and dipping the turmeric paper in the serum. Another simple test for the presence of boric acid consists in putting about $ oz. of milk in a glass, adding half its bulk of phenol-phthalein, and dilute caustic soda solution drop by drop, with constant stirring, till a faint permanent pink colour is produced. Some of the pink-coloured milk is poured into two test tubes. To one tube is added an equal bulk of water, and to the other an equal bulk of a neutral mixture of 1 part pure glycerol and 1 part water. In genuine milk both tubes remain pink, and the colours are practically identical, but in the presence of boric acid the water tube becomes darker in tint, and the glycerol tube much lighter—usually quite white. If boric acid be present, 25 to 50 grammes of milk should be taken for estimation. After addition of about 0-2 gramme caustic soda, the milk is evaporated and thoroughly charred by ignition ; the residue is extracted by dilute acetic acid, and well washed with as small a quantity of water as possible; the solution is filtered into a small flask, to which a condenser is fitted, and ESTIMATION OF BORIC ACID. : (hh 5 distilled to dryness into about 10 c.c, of strong ammonia ; eight successive portions of 10 c.c. each of methyl alcohol are added and distilled off. : About 1 gramme of lime is ignited in a capacious platinum basin in a muffle at the highest temperature attainable, and the basin and lime weighed. The ammoniacal distillate is now added and the liquid evaporated on the water-bath ; the basin is again ignited in a muffle and weighed. The increase of weight repre- sents the boric anhydride. Hehner prefers the use of a measured quantity of sodium phosphate solution of known strenyth for fixing the boric acid instead of ammonia and lime. He distils directly into the sodium phosphate solution, evaporates and cautiously ignites. The weight of the residue of pyro-phosphate obtained from an equal measure of sodium phosphate solution is subtracted from the weight of the residue; the difference represents boric anhy- dride. It is necessary, however, to ignite very cautiously, as sodium phosphate is liable to spurt. Thompson has shown that boric acid may be titrated with caustic alkali, using phenol-phthalein as indicator, provided at least 30 per cent. of glycerol be present. His directions are : J or 2 vrammes of caustic soda are added to LOO e.c. of milk and the whole evaporated to dryness in a platinum dish. The residue is thoroughly charred, heated with 20 cc. of water and hydrochloric acid added drop by drop till all but carbon is dis- solved. The whole is transferred to a LOO c.c. flask, the bulk not being allowed to get above 50 to 60 ce, and half a eramme of dry calcium chloride added. To this mixture a few drops of phenol-phthalein solution are added. then a 10 per cent. solution of caustic soda, till a permanent pink colour is perceptible, and, finally, 25 c.c. of lime water. In this way all the phosphoric acid is precipitated as calcium phosphate. The mixture is made up to LOO ¢.c., mixed, and filtered through a dry filter, To 50 cc. of the filtrate (= 50 ¢.c. milk) normal sulphuric acid is added till the pink colour is gone, then a few drops of methyl orange, and the addition of acid continued until the yellow is just changed + to pink. “caustic soda solution is added till the liquid assumes a vellow tinge, excess of soda being avoided. At this stage all acids likely to be present exist as salts neutral to phenol-phthalein, except borie acid and a little carbonie acid. which last is expelled by a few minutes boiling. The solution is cooled, a little more phenol-phthalein added, and as much elycerol as will give at least 30 per cent. of that substance in the final solution, and titrated 4) with caustic suda till a permanent pink colour 1s produced. YS 86 ANALYSIS OF MILK. = Each c.c. of = caustic soda solution is equal to 0°0124 gramme crystallised boric acid or 0-0070 gramme boric anhydride. ae Phosphoric acid can be separated from boric acid by precipi- tation as calcium phosphate, if not more than (2 per cent. of crystallised boric acid be present. As excessive heating is apt to drive off boric acid, it is necessary to carry the charring so far only as will give a colourless solution. This method tends to give rather low results, as a portion of the boric acid remains in the calcium precipitate, while, on the other hand, all the phosphoric acid may not be removed. Shrews- bury recommends that after charring the milk, and dissolving the ash in acid, a little phenol-phthalein solution be added, and then dilute caustic soda solution and calcium chloride solution alternately till a permanent pink is produced. The filtrate is then titrated with acid using methy! orange as indi- cator, and then using phenol-phthalein with alkali in the pre- sence of glycerol. If more than 17 c.c. . alkali is used the precipitate should be dissolved up and reprecipitated, the second filtrate titrated, and the results added to the first titration; if necessary, the process should be repeated. Allen and Tankard have devised a method for the estimation of boric acid, which consists in evaporating the liquid to be tested to dryness with a few cubic centimetres of 10 per cent. calcium chloride solution; in the case of milk or cream it is advisable to add just sufficient alkali solution to neutralise it to phenol-phthalein. To 10 to 25 c.c., add 4 of its bulk of 10 per cent. calcium chloride solution, and just sufficient alkali to neutralise to phenol-phthalein; evaporate to dryness: ignite at a gentle heat till thoroughly charred, boil the residue with 150 c.c. of distilled water, and filter the liquid. The filter is returned to the dish, and the residue ignited till white at a moderate temperature, and boiled with a further 150 ¢.c. of water. The liquid is allowed to stand over- night, and is filtered cold; the mixed liquids are evaporated to a volume of 25 to 30 ¢.c.: and after cooling neutralised with a acid, using methyl alcohol as indicator. An equal volume of glycerol is added, and a little phenol-phthalein, and the solution titrated with = caustic soda (free from carbonate). The volume of io caustic soda required by an equal volume of glycerol is subtracted from the amount used, and the remainder multiplied by 00062 will give the weight of H,BO,. ESTIMATION OF BORIC ACID. 7 The author and Miller have found that it is quite unnecessary either to evaporate the milk, ignite it. or to use any indicator other than phenol-phthalein; the method is—-to a measured or weighed quantity of mill (10 ¢.c. suffices) add half its bulk of a 05 per cent. solution of phenol-phthalein. and run in alkali till a pink colour appears, boil, and titrate back while still boiling with acid solution till white, and finally with = alkali till faintly pink. The colour, though faint, is quite distinct, and no attempt should be made to obtain a pronounced pink colour, Add 30 per cent. of glycerol, and continue the titration with ay alkali without further heating; subtract, if necessary, the glvcerol blank, and the alkali used for the final titration multiplied by 00062 gives the boric acid. Cassal and Cerrans find that an intense magenta-red colour is produced on treating solutions containing boric acid with curcumin—or ordinary turmeric itself—and oxalic acid. and drying the mixture on the water-bath. The colour is different from that obtained by the application of the ordinary turmeric test for boric acid and the reaction is far more delicate, extremely minute quantities of boric acid being easily detected. The colour is practically permanent for several hours—not less than ten or twelye—and fades very gradually on long keeping. The colouring matter is readily soluble in alcohol and ether without alteration, but is destroyed by the addition of water in excess. On treatment with alkali an intense blue colour is obtained. which is different from that obtained on treating the * rose- red” colouring matter formed in the ordinary turmeric test. with alkali. In applying the test for the detection of free or combined boric acid in milk and other food products it is con- venient as a rule to operate on an ash. The ash is treated with a few drops of (1) dilute hydrochloric acid, (2) saturated solution of oxalic avid, and (3) alcoholic solution of curcumin or turmeric, and the mixture dried on the water-bath and taken up with a little alcohol. In cases where the amount of boric acid is very small the substance, the ash of which is to be operated upon, should be made alkaline with solution of barium hydroxide prior to evaporation and incineration. Caustic potash and caustic soda and salts of potassium and sodium in large amounts interfere with the formation of the colouring matter. They also apply this reaction for the quantitative estimation of boric acid. In the case of milk. from 15 to 20 grammes are weighed out, transferred to 100 c.c. Hask. and made up to 100 c.c. with water. Ten c.c. (or more, according to circumstances) are transferred 88 ANALYSIS OF MILK. to a porcelain dish and mixed with 15 to 20 grammes of purified sand (obtained by igniting “silver sand,” boiling this with 25 per cent. hydrochloric acid, and thoroughly washing and drying). The use of such a medium as sand is essential in order to secure intimate and complete contact between the reacting substances at the drying point—which is the point of reaction. The mixture is made alkaline with barium hydroxide, and evaporated to dryness. Two c.c. of a 1 per cent. alcoholic solu- tion of curcumin are added, and the mixture again evaporated to dryness, the mass being stirred from time to time to ensure thorough incorporation. To the mixture is now added 1 c.c. of a solution containing 25 c.c. hydrochloric acid and 10 grammes of oxalic acid in 100 c.c. of water, and the mass is again dried. The same operations are carried out with 10 c.c. of a standard solution of boric acid [1 ¢.c. being equal to 0-1 milligramme of boron trioxide (B,O.)]. The colour having been obtained in both cases, the sand is extracted with ordinary alcohol. The coloured solution obtained from the milk is diluted with alcohol or methylated spirit until the colour is of the same degree of intensity as that formed from the standard ; and the amount of boric acid is arrived at by an obvious calculation. The colours are compared in two tubes of the same internal sectional diameter (about 1 centimetre) placed vertically against a white porcelain plate. On comparing the two solutions it will occasionally be found that a certain amount of orange tint is exhibited by one or the other, due to the presence of curcumin in slight excess. When this is observed the tints must be made the same by the cautious addition of solution of curcumin to the solution which does not show the orange tint. The result of a number of experiments made with known amounts of boric acid and borates show that the process is reliable and accurate. Estimation of Citric Acid in Milk.—The proteins are precipi- tated by acid mercuric nitrate (p. 90) and a measured volume of the clear filtrate exactly neutralised with dilute caustic soda solution, using phenol-phthalein as indicator. A white precipi- tate of mercury and calcium phosphate and citrate is thrown down, collected on a filter, and washed with water ; it is removed from the filter, suspended in water, and a little dilute hydro- chloric acid added ; sulphuretted hydrogen is passed through to precipitate the mercury as mercuric sulphide. After filtration, the the solution is boiled to remove sulphuretted hydrogen, and, after the addition of a little calcium chloride, cooled. It is then care- fully neutralised, phenolphthalein being used as indicator ; the ESTIMATION OF CITRIC ACID. 39 precipitate of calcium phosphate is filtered off, and the solution boiled and concentrated to a small bulk; the calcium citrate is thus precipitated. This should be washed with boiling water, collected on a small filter and ignited. To the ignited residue an excess of standard hydrochloric acid is added and the excess titrated back with standard alkali, methyl oranee being the best ES indicator, Each cubic centimetre of a hydrochloric acid used represents 00064 vramme of citric acid. The result must be corrected for the volume of the fat and protein thrown down as directed under milk-sugar. Gowing - Scopes’ Method. — L. Gowing-Scopes has investi- vated the method originated by Denigés, which consists in oxidisine citric acid to acetone dicarboxylic acid, and the con- version of this into an insoluble basic mercury salt. He finds that, to obtain exact results, strict attention must be paid to details of manipulation. For the estimation of citric acid in milk, the clear filtrate obtained by adding acid mercuric nitrate to milk as for the estimation of milk sugar is used ; 10 c.c. of this is exactly neutral- ised with alkali, using phenol-phthalein as indicator , a precipitate will form. but this will be redissolved on the addition of 10 c.c. of a reagent prepared hy covering 51 grammes of mercuric nitrate and 51 erammes of manganese nitrate with 6S c.c. of strong nitric acid, and after the addition of 100) cc. of water to dissolve the salts, making up the volume to 250 c.c. and filtering. The solution is diluted to 200 c.c., and boiled under reflux for three hours, filtered through a weighed Gooch crucible, and the precipitate well washed with cold water: the deposit on the sides of the fask may be removed by addiny 1 or 2 ¢.c. of 1 per cent. nitric acid. and rubbing with a red: after drying for tive hours the precipitate is weighed. The colour of the precipitate should be nearly white ; if it is yellow. this is due to the presence of basic salts, and the result will be high. The weight of the precipitate multiplied by 0-1667 will sive the amount of citric acid, and in calculating the percentage in the milk, the corrections for the volume of the precipitated proteins and fat must be made as in Vieth’s method of milk- suuar estimation. The method given above departs slightly from Gowing-Scopes’ original method, as. owing to the presence of mercury m the filtrate. shehitly more mercuric salts are present than he prescribes, but his researches have shown that variations of the amount of mercury used have far less influence on the results than vari- ations in the other ingredients of his reagent. and the small 90 ANALYSIS OF MILK. excess of mercury present does not necessitate any appreciable variation of the factor. Estimation of Milk-Sugar.—Milk-sugar is generally estimated indirectly, as it is not possible to isolate it quantitatively from milk in a state of purity. The following method may, however, be used to obtain an approximate determination of the milk- sugar :— By Alcohol.—To 10 ¢.c. of milk add 20 c.c. of 90 per cent. alcohol, well mix and filter; of the filtrate take 10 or 15 c.c., evaporate to dryness on a water-bath and dry at 100° C. (212° F.) till the weight is constant. Ignite the residue and weigh the ash. The weight of the residue less the weight of the ash will give the weight of the milk-sugar. The volume of the aqueous portion must be calculated; on mixing alcohol and water a contraction takes place ; this with the quantities given is 0-4 c.c. ; the volume occupied by the protein is on the average 0°25 c.c. ; the volume of the fat is obtained by multiplying the percentage by weight by O11, The percentage of milk-sugar is obtained by the following formula :— M “ _— “HD . _ BW OU as ae aoe x D where «x =number of ¢.c. taken for estimation of residue. D = specitic gravity of milk. F = percentage of fat in milk. R = weight of residue. A= fs ash. M = percentage of milk-sugar. This method has a tendency to yield results about 0-2 to 0°3 per cent. too high. By the Polariscope (Fig. 6).—The quickest method of milk-sugar estimation is by the polariscope; before the milk can be polarised it is necessary to remove the fat and proteins completely which interfere either by making the solution too opaque for reading or by polarising to the left. Wiley’s Method.—The investigations of Wiley have shown that mercury compounds are the most efficient for this purpose, of which “acid mercuric nitrate ” is the most convenient. This is prepared as follows :—Mercury is dissolved in twice its weight of nitric acid of specific gravity 1:42, and, after solution, an equal bulk of water is added. Basic lead acetate has also been used to remove fat and protein, but Wiley has proved that the results are not accurate, owing to the incomplete removal of protein. Still more inaccurate is the use of acetic acid, followed by boiling, which has been recom- mended by Blyth. ESTIMATION OF MILK-SUGAR. G1 Wiley-Ewell Method.—Wiley and Ewell give the following method as the best for estimating milk-sugar by the polariscope :— They used a Schmidt & Hensch polarimeter, with which 200 millimetres of a solution of 32:91 grammes of milk-sugar in 100 c.c. read 100 divisions of the scale. They take 65°82 grammes of milk, add 10 ¢.c. of acid mercuric nitrate solution (in this case the solution of mercury in nitric acid is diluted with 5 volumes of water), and dilute to 100 cc, A similar quantity of milk is taken, 10 c.c. of acid mercuric nitrate added and diluted to 200 cc. Each of these solutions is well mixed, filtered. and polarised in a 400 mm. tube. Fig. 6.—Polariscope. Calling the reading of the solution obtamed from 100 c¢.c. v, and that obtained from 200 e.c. y, the true percentage of milk- ty Ha — y)’ The double dilution does away with any correction for the volume of the precipitated fat and protein. The rationale of the process lies in the fact that, while the percentage of milk- sugar and the volume of the precipitate are constant, the total volume varies. sugar 1s 92 ANALYSIS OF MILK. Let m be the percentage of milk-sugar, and v the volume of precipitate ; n we _ _100 then a= 4m x Tee (1) 200 and Y= BYU ee (2) gin? wv _<_-100 200 No ay (100 =v) (200 =) w a 5 4(x-y) a( dmx — 2m x Pe ) 100 200 -v =. Sm? _x 100 x 200 ~ 4(4m x (200—v) x 100—2m x (100-7) x 200) = ; 8m? < 100 «x 200 ~ 4(4m x 100 x 200-2am x 100 x 200-4m x 100v + 2m x 200v) Ps ~ 8m The volume may he calculated thus :—From (1) we see that 100-» = 4m x 100 or v= 100~ "= 100 dry ~ 100 da(u-y) =109- 7x00 uy _ 100. - 200y cae = 100- which may be similarly deduced from (2). This method not only allows of an estimation of milk-sugar to be made in milk without correction of any kind, but enables the volume of the precipitate of fat and protein to be calculated. The author, in conjunction with Boseley, has shown that the experimental error of Wiley and Ewell’s method is, however, very appreciable; and, though correct in principle, it is not so accurate in practice as originally claimed. It is not necessary to adhere strictly to the volumes given ; by a modification of the formule the percentage can be cal- culated from any two dilutions, but the greatest delicacy of Wiley and Ewell’s method—i.c., the point at which the influence of unavoidable errors in reading is least—is obtained when the volume of water added to the more dilute solution is equal to the volume of the milk taken, less that of the fat and precipitated protein. ESTIMATION OF MILK-SUGAR. 93 Vieth Method.—Vieth, when using the small Mitscherlich half-shadow polarisecope made by Schmidt and Heensch, prefers to add the stronger mercuric nitrate solution, described above, direct to the milk, and to polarise the resulting filtrate. He finds the volume of precipitated proteins from 100 c.c. of milk to amount on the average to 3 c.c., and, consequently, adds 3 c.c. of acid mercuric nitrate solution to allow for this. The method is carried out as follows :—Measure 50 c.c. of milk into a small flask, add 1°5 c.c. of acid mercuric nitrate, and well mix by shaking violently ; pour the mixture on to a filter, and fill a polarimeter tube with the filtrate; polarise, and correct the reading for that obtained in a blank reading—v.e., by reading a tube filled with water. As the [¢], of milk-sugar is 52°5 , the reading, if in angular degrees, can be converted into percentages of milk-sugar by the following formula— m — 100 100 B25 7 Where m = number of grammes of milk-sugar per 100 c.c. of solution polarised, 2 = length of tube in millimetres. r= reading in anzular degrees, Tf a tube of 198-1 millimetres be used (these tubes are sup- plied with the instrument used by Vieth), the formula becomes i we POL If the length of the tube be 200 millimetres, the formula is The resulting figure representing milk-sugar in the solution polarised must be submitted to correction. The volume of the liquid from which the fat and protein have been precipitated is the volume of the milk plus that of the mercuric nitrate minus that of the protein precipitate and fat. As the volume of the mercuric nitrate was purposely made equal to that of the protein, both of these may be neglected, one compensating for the other. Taking the volume of the milk as 100 ¢c.c., the volume of fat in this will be the percentage by weight of fat multiplied by the specific vravity of the milk, divided by the specific gravity of the fat. The milk-sugar may be either calculated as hydrated or anhydrous sugar, but it is usual to calculate it in milk analysis as anhydrous sugar. 94 ANALYSIS OF MILK. The following formula expresses the percentage of anhydrous milk-sugar in the milk when a tube of 198-4 mm. is used :-— y, Ld 100 pear oF 0: “93. Las nS oy @ Gg qx O%: m\ = percentage of anhydrous milk-sugar by weight, rv = reading, , F = percentage of fat by weight, d = specific gravity of milk. For the expression it is usually exact enough to employ Fd 0°93 the expression F x I-11. As an ee let us suppose that, using a 1984 mm. tube 5°5 4° 1 5° 1 x 09545 x - Ta i aD x 0°95 = + d8 per cent. mn = Vieth states that when cream is analysed by this method, it is necessary to dilute with an equal bulk of water, the results being, of course, doubled. Richmond - Boseley Method.—The author,.in conjunction with Boseley, has shown that the calculation necessary in Vieth’s method can be eliminated by adding to 100 c.c. of milk (a) A quantity of water in ec. equal to ,'5 degree of specific gravity. ( ”» os s ~=—oo-~|~Ssé thee fat x 2°11. (c) oh se », to reduce scale readings to perceutages of milk-sugar, (d) 3 ¢.¢. of acid mercuric nitrate. The percentage of milk-sugar can be read off directly in scale readings. The values of ¢ are:—For poluriscopes reading angular degrees— With 198-4 mm. tube, 10:0 c.c. 2 200 ” 10°85 ” s, 900 3 10°85 ,, (divide readings by 2-5). For the Laurent sugar scale (100° = 21:67 angular deyrees)— With 200 mm. tube, 2°33 c.c. (divide readings ty = Be 400 *3 2: 33 ? ( ” ” Led 500 ” 2: 33 » ( ” ” 13 5) For the Ventzke scale (100° = 34-64 angular degrees)— With 200 mm, tube, 6°65 c.c. (divide readings by 3). >> 400 ” 605, ( ” ” 6). »» 500 » 6°65 4, ( 9 ” 75). The author has recently shown that mercuric nitrate does not precipitate the whole of the proteins, and that a small further ESTIMATION OF MILK-SUGAR. ) precipitate is obtained by the addition of phospho-tungstic acid ; the difference in the percentage of milk-sugar found after adding phospho-tungstic acid is, however, very small, and it is usually only. in concentrated milks that it exceeds the experimental error. For exact estimations add to a measured volume of the mercuric filtrate ,!, of a 10 per cent. phospho-tunystic acid solution and .j, of 1:1 sulphuric acid; filter. polarise, and multiply the readings by Ll. Deniges’ Method.— Denigés objects to the use of mercuric nitrate because it necessitates the use of a elass polarimeter tube, brass bein attacked by the solution, and prefers the use of meta-phosphoric acid to precipitate the proteins. His method is as follows :—Prepare sodium meta-phosphate by carefully heating sodium-ammonium-hydrogen phosphate (microcosmic sult) in a platinum dish, till it is completely fused and no longer evolves gas. Pour on a cool plate, break up, and preserve in a stoppered bottle. Prepare a 5 per cent. ayueous solution by boiling 5°7 grammes of the finely powdered salt with 50 c.c. of water for five minutes, at the expiration of which time solution should be complete. Add immediately 50 c.c. of cold) water, cool under a jet of water, and make up to LOO cc. Twelve per cent. of the meta-phosphate is converted into ortho-phosphate by the boiling, and this is allowed for by taking 5-7 grammes instead of 5 erammes. Add 25 c.c. of this freshly prepared solution to 10 c.c. of milk, then 60 cc. of water, and 0°3 c.c. of acetic acid; make up to 100 c.c, and filter ; after rejecting the tirst few drops, fill a polari- sation tube with the filtrate. A 500 mm. tube is to be used, if possible, in preference to one of less length. It is hardly neces- sary to make any correction for the volume of the precipitate on account of the great dilution. As only 10 ¢.c. of milk are taken and diluted to 100 c.e¢., a very good polariscope must be used if accuracy is required. Unless glass polarisation tubes are unobtainable, the use of mercuric nitrate is preferable; an advantave of employing mercuric nitrate is that citric acid can he estimated in the same solution. The proteins may also be precipitated by adding to milk an equal volume of a saturated solution of picric acid containing 1 per cent. of acetic acid. Fehling’s Solution Method.— £ 215 83 62 30 22 2 7 2 125 oe ao " 6 2 oak 1 54 Sl Hee e 3 1 wai 1 26 8-0 15 7 ec ee 3 tee 25 79 10 2 2 1 1 16 78 5 1 was ea 6 77 3 2 ae eA es 79 2 1 1 a -_ 4 75 sis ida eas ee 2 2, 73 ma wie 1 1 71 ies ea ui 1 66 1 aa 1 6:2 1 1 61 ‘ 1 1 49 1 1 The samples yielding below 7 per cent. of solids not fat were all obtained from one cow. The following are analyses on different dates of her milk :— TABLE XXV.—VaprtaTIons IN SoLtips Not Far 1n MILK FROM THE SAME Cow. : < i a2 a ¢ ; A] me as ae a5) a5 | ae ae <5 (Sareea = ms evel Per ct. | Perct. | Perct. | Perct. | Perct. | Perct. | Per ct. | Per ct. Total solids, 14:0 | 12°8 | 14:3 | 16°7 | 11-0 | 14°8 | 15-1) | 1271 Fat... Z 49 3°8 9-4 | 105 49 82 | 63 32 Milk-sugar, ee es Bae as 191) 3°26, jog Protein, are ae aie “2 3°35} 3°32 BEB sae al! Ge . 0-78| 0-76 0-86) 0-76 .. | Solids not fat, . o1 90) 4-9 6:2 | Ol 66 | 8s 8:9 { i | Table XXVI. gives the maximum, minimum, and average percentages of total solids, fat, and solids not fat in the milk of cows of different breeds, obtained from analyses of the milk of cows kept on the Aylesbury Dairy Company’s Estate at Horsham. COMPOSITION OF DIFFERENT BREEDS. 157 TABLE XXVI.—Sotips 1x Mitk or Cows oF DIFFERENT Breeps (Vieth). Total Solids. Fat. Solids not Fat. Breed. Max. Min.| Aver. | Max. Min. | Aver.) Max.| Min. Aver. p.ct. p.ct.| p.ct. |p. ct.|p.ct.|p. ct.| p. ct.| p. ct. / p. ct. Dairy Shorthorn, |18°7 | 10-2 | 12-90] 10-2) 1:3] 4:03] 106] 7-6 887 Pedigree ,, 16°83 105 | 12°86} 7°5/ 1:9) 4°03] 9°8| 76 | 8-83 Jersey, . »« « {199/110} 14°89] 9:8] 2:0) 5°66] 10-4] 8-1 | 9-22 Kerry, . . . | 186/106] 13°70) 105} 1:8) 4°72] 106] 4:9 | 8-93 Red Polled, . . | 16:2) 9°7] 13:22] 66] 2°5| 4:34] 10-2] 7-1 | 8-88 Sussex, . . . |17'4:11°5]14:18] 76] 2:9] 4:87] 103] 8:4 | 9°31 Montgomery, . | 16°1:102/12°61} 65) 1:4! 3:59] 10:0] 7-9 | 9-02 Welsh, . . . {176:11°9/14:15] 8:3! 3:0|4:91|) 96] 8-9 | 9-24 i The figures below (Table XXVII.) were obtained at the New Jersey State Agricultural Experiment Station. TABLE XXVII.—Composirion or Mrtk or DirreRENT Breeps or CartLe. Breed. Total Solids. Fat. Milk-sugar. Benin Ash. Per cent. Per cent. Per cent. Per cent. , Per cent. Ayrshire, . . 12-70 3°68 4°84 348 0°69 Guernsey,. . . 14:48 5:02 4°80 3°92, 0-75 Holstein, . . . 1212 3°51 4°69 328 | O6t Jersey,. . . . 14°34 4°78 4°85 3:96 75 Shorthorn, . 12°45 3 65 4:80 327 | 0-73 | Fleischmann also gives the following figures :— Breed. Total Solids, Fat. Solids not Fat. Per cent. Per cent. Per cent, Dutch, ‘ - 11-91 3-23 8-68 German, - 7 12:25 3°40 8-85 Bonnema gives for North Dutch or Frisian cows the following averages :— Total solids. Fat. Sugar. Protein. Ash. Solids not Fat. 115 3-0 4:3 3:5 0-7 85 Liverseege gives, using analyses by James Bell, figures for the composition of the milk yielded by cows of different breeds; he notes that in some cases the number of samples is too small to be of much use. 158 NORMAL MILK: ITS ADULTERATIONS, ETC. TABLE XXVIII.—Sotips iy Mitk oF DirFERENT BREEDS OF CaTTLE (Bell). Breed. ' Total Solids. Fat. Solids not. Fat. = Per cent. | Per cent. Per cent. Sussex, . 1231 3°39 ; 8:92 Welsh, . | 13°55 4:40 915 Guernsey, - . ef 14:46 516 9°30 Jevsey,. 6 ee | 14-65 5-43 9-22 Kerry, . : 3 13°54 4°67 8°87 North Devon, y 3 13°11 3°43 9°68 Dutch, . . i ; 12°40 3°75 8:65 Ayrshire, . s i 13°46 4-24 9:22 Shorthorn, ; ? 12°78 3 92 8°86 I Variations of Fat in Different Churns.—When milk is divided into portions, as is the case when it has to be transported by railway, considerable variations in fat are sometimes noticed. As examples, the following analyses may be quoted :— TABLE XXIX. Series I. Series II. Specific gravity, 1:03845 1:0340 1-0320 1:0325 1°0320 1-010 p. ct. p. ct. p. ct. p. ct. p. ct. p. ct. Total solids, . 11°28 11°66 14:16 11:22 12-42 =—-13°42 Fat, . . . 2°10 2°50 5:10 2°60 3°70 4:80 Solids not fat, . 9°10 9°16 9:06 8-62 8:72 8°62 Seasonal and Monthly Variations.—Distinct variations according to season are found; these will be shown by Table XXX., which gives the mean monthly averages of milk for the past seventeen years. The year, roughly speaking, can be divided into four periods :— (1) November, December, and January ; the milk is rich, both in fat and solids not fat. (2) February, March, and April; the solids not fat do not show appreciable diminution, but the fat becomes less in quality. (3) May, June, July, and August; the fat is low, though there is a tendency to rise at the end of the period. In July and August the solids not fat are below the average. (4) September and October ; an improvement in quality both in fat and solids not fat is noticed. These periods correspond approximately to the seasons; winter milk is of very good quality, while summer milk is the poorest ; the spring and autumn are transition periods. The quality varies in an inverse ratio to the quantity yielded. AVERAGE COMPOSITION. 159 In the analyses below (Table XXX.) the specific gravity has always been determined by a lactometer; the fat determinations were made by the Gerber method. The total solids have been calculated by the formula devised by the author. TABLE XXX.—Mean Montuiy AVERAGES oF MILK. (1897-1913.) t | Month. | Specific Gravity. | Total Solids. | Fat. vaeoss Per cent. Per cent. Per cent. January, : 1-0323 12°75 3-78 8-97 February, : 1-0323 12°68 3-72 | 8-96 March, . 4 1-0322 ; 12-64 3°68 8-96 April, . . 1-0322 12-56 365 891 May, «© « 10323 12-52 3:57 | 8:95 June, ‘ . 10322 12-43 3:52 § 891 July, ‘ 4 1:0317 12-40 3°63 8:77 August, . é 1-0315 12-51 3°75 8°76 September, ‘ 1:0318 12-69 3°84 8-85 October, 4 J-0321 12:86 3°92 8°94. November, : 10321 12-93 3:97 8-96 December, F 10322 12:86 3°90 8:96 Average, . 1-0321 12-65 3-74 8-91 Daily Variations.—It has been found that the percentage of fat varies slightly according to the day of the week, as is shown by the following figures :— Day, Mon. Tues. Wed. Thurs. Fri. Sat. Suu. Per cent. fat, 3-70 3°78 3°75 375 3-75 3°73 374 It is seen that Monday’s milk is the lowest in fat; this is probably due partly to a disturbance in the quality arising from the interval between milking on Sunday night and Monday morning not being identical with the usual interval, and partly to the influence of the Sunday holiday on the milkers, rendering them rather more careless about stripping the cows on Mondays than on other days. Morning and Evening Variations.—In England it is the custom to milk cows twice a day; the quality is not the same at both meals, the evening milk being almost invariably richer in fat than the morning milk. In dairies where it is the custom to leave an interval of twelve hours between the milkings this is far less noticeable than in those where there is an interval of nine to ten hours between the morning and the evening meal, and fourteen to tifteen hours between the evening and the morning meal. 160 Table XXXL, NORMAL MILK : ITS ADULTERATIONS, ETC. giving the mean monthly average of morning and evening milk for “the past seventeen years, will show the average difference. The mean intervals of milking were 10°8 and 13°2 hours. TABLE XXXI.—Composirion or Mornine anp Eventne MILK. (1897-1913.) | Merning Milk. Evening Milk. 1 Month. | |. [ are Specific | Total j.44, | Solids | Specific Total pat, | sotias Gravity. | Solids. not Fat.: RGTAVINY. Solids. ise Fat. a t ! | a | January, 1-:0324 | 12-58 3-62 | 8-96 | 1:0322 12-92 3:94 | 8:93 February, 1-0325 | 12-52 | 3-56 | 8-96 | 10322 12°85 3:89 | 8-96 March, 1:0324 | 12:46 | 3-51 | 8-95 | 1: 0320 ! 12°81 3-85 | 8-96 April, 1-0323 | 12-40 3-48 | 8-92 1-0321 _ 12 73 3°83 | 8-90 May, . | 10326 | 12-27 | 3:33 | 8-94 | 10320 | 12-75 3-80 | 8-95 June, i 1-0325 | 12-21 3-29 | 8-92 | 1:0320 12°65 3-76 | 8-89 July, 1-0320 | 12-24 3-46] 8-78 |1:0314 12-56 3°80 8-76 August, 1-0318 | 12-31 , 3-55 | 8-76 | 1: 0313 12:70 3:95 8-75 September, 1-0320 | 12-49 | 3-63 | 8:86 10316 12-89 405 8-84 October, 1-0322 | 12°67 | 3-72 | 8-95 1:0319 13:04 4:11 8-93 November, . | 1:0323 | 12-77 | 3:80 | 8-97 .1:0320 13:09 4:14 8-95 December, . | 1:0324 | 12-72 3-75 | 8-97 | 1:0321 13:01 4:05 8-96 Average, . 1-0323 | 12-47 3:56 | 8-91 1:0319 12-83 3:93 10 | ; I | Variations on Partial Milking.—The first portions drawn from the udder are known as “fore milk,” the last portions as ** strippings ” of fat in strippings. the udder is very different from the last portions. ; It is not unusual to find more than 10 per cent. The quality of the milk first drawn from Boussingault has recorded the following analyses of milk drawn from a cow in portions :— Portion i 2 3 4 5 6 si ; Per cent. | Per cent. | Per cent. | Per cent. | Per cent. | Per cent. Total solids, 10°47 10°75 10°85 11-23 11°63 12°67 Pity a. + 170 176 2°10 2-54 3:14 4:08 Solids not fat, 8-77 8:99 8:75 8-69 8°49 8°59 Heaton has also given a remarkable analysis of a partial milking ; it contained only 0°26 per cent. of fat. It is sometimes noticed that a cow, through restlessness or nervousness, holds back her milk, especially o the surroundings COLOSTRUM. 161 are strange. Thus Dyer has recorded an analysis of milk obtained from a cow at an agricultural show which contained 1°85 per cent. of fat; the next day the milk was normal, containing 3°64 per cent. of fat. Many, if not all, of the very low fats recorded in Table XXIV. on p. 156 are due to this cause. Colostrum.—The name “ colostrum ”’ is applied to the secretion of the udder before (and immediately after) parturition. Las- saigne pointed out that an albuminous liquid commenced to form sometimes two months before parturition. This secretion, accord- ing to Houdet, often appears under two forms—a brownish, viscous, honey-like product, and a lemon-yellow, non-viscous liquid; the two often co-exist in the same animal, the earlier milkings furnishing the first, and the later the second. The viscous secretion is curdled by heat, and precipitated by acetic acid, mercuric chloride, and alcohol, but not curdled by rennet. The analysis is Pour cent. Water, . : . * . ‘ ‘ » 63-14 Soluble protein, . : ‘: : : . 22-74 Colloidal ,, : ‘ . F ; . 14:12 Ash, - ; f ‘ é ‘ 7 . trace The non-viscous secretion contained more water and less soluble protein than the viscous secretion, and gave a barely appreciable precipitate with mercuric chloride and alcohol, but was coagulated by heat and acetic acid and unaffected by rennet. One hundred cubic centimetres contained Fat, . ‘ : & . : . O-15 gramme. Sugar, ; - Z ‘ ‘ « 80 i Soluble proteins, P . 1:38 ey Colloidal ,, 2 ‘ ‘ . 439 ,, Calcium phosphate, . ; : . O11 “5 Other salts, é : ‘ . 0:38 ss Total solids, ‘i . 721 ‘ The composition of the fluid secretion approaches more nearly to that of milk. Four or five days before parturition the secretions are replaced by colostrum proper. True colostrum is an opaque yellow liquid of pungent taste : sometimes blood is present, which shows its presence by a reddish colour. It is curdled by heat, acetic acid, mercuric chloride, and rennet (though the action of this is not so rapid as with milk). It has a slimy, viscous appearance, and, if left to stand, has a tendency to separate into two layers. The proteins probably consist of casein, albumin, ge and 162 NORMAL MILK: 1TS ADULTERATIONS, ETC. globulin, while lecithin, cholesterol, tyrosine, and urea are present. Proteoses and peptones have been found. The sugars of colostrum consist of milk-sugar, dextrose, and, possibly, other sugars. The fat differs from that of milk; the melting point is high (40° to 44° C.), and the amount of volatile acids low. Pizzi found that a few hours (3 to 6) before parturition the Reichert-Wollny figure of the fat was 4°4 to 4°7, and six hours after calving 6°2 to 6°3; a rapid increase was noticed, and in from three to six days a normal figure was reached. The ash of colostrum has, according to Fleischmann, the following composition :— Per cent Potash, . ‘ ¢ F . ‘ : é . 723 Soda, . c i a ‘ ‘ i . 5°72 Lime, . ‘ ; F : : 34°85 Magnesia, . 5 * 5 . : . 2°06 Ferric oxide, : . ; F i . 0°52 Phosphoric anhydride, ‘ . : ‘ 41°43 Sulphuric 3 ‘ : ‘ . 3 . O16 Chlorine, ‘ : . 2 ‘ Fe . 11:25 103 ‘22 Less oxygen equivalent to chlorine, . - 822 100-00 The best defined characteristic of colostrum is the presence of the ‘‘corps granuleux’’ of Donné, which consist of clusters of cells like bunches of grapes. These are from 0°005 to 0°025 milli- metre in diameter, and are easily detected under the microscope. They do not disappear entirely from milk till three weeks after calving, according to Henle. The specific gravity of colostrum is from 1:046 to 1:079 at 15° C. (59° F.), and averages 1-068. Engling gives the following composition :— Percent. Percent. Per cent. Water, * . 76:60 to 67-43 average, 71-69 Fat, . ‘ . 1:88 ,, 468 35 3°37 Casein (?), 3 2-64 ,, 7:14 55 4:83 Albumin (*), 11-18 ,, 20-21 2 15°85 Sugar, ‘ F 1:34 ,, 3°83 se 2-48 Ash, ‘ z > LIS ,, 231 3 1-78 Change of Colostrum to Normal Milk.—The composition of colostrum changes rapidly after parturition. Houdet gives the following figures as illustrating the change :— COLOSTRUM. 163 Soluble | Colloidal Calcium Other Fat. \Proteins.| Proteins. Phosphate Salts. Sugar, { : Per ct. | Per ct. Per ct. Per ct. Perct . Per ct. Six days before calving, 0°50 | 2:35 0-47 | 17-43 0-44 | 0-36 Four ,, es 3-01 | 3:17 | 0-45 | 12:08 0-47 | 0-40 Immediately after,, | 3-14 | 270 | 0-25 | 14:53 | 0-46 | 0-42 These figures show a sudden increase in the amount of proteins over that contained in the fluid secretion described above. Houdet ascribes this to a diversion to the udder of nutritive material which up to this time had been supplied to the fcetus. An increase of fat and a decrease of soluble proteins are also observed. The colostrum from another cow was examined at intervals after parturition with the following results (Table XXXII), which show the gradual transition into normal milk :— TABLE XXXII. eae or CoLosrruM Tro NormaL MILK. Soluble ea ist taled WEL ss Lite: ee, | sige ee Colloidal Calcium — Other | ! Proteins. Phosphate Salts. ‘Per ct., | Per ct. . Per et. Per et Per ct. | Per ct. | Immediately after calving 5-69 3:30 | O51 |» 14-05 OSL 0-54 © 1 day » og) 48 05-098 5210-43043 | 2 days yo T0432) 1-98 352 O43 O45 30, » on 140) 426) 241 345 00—~COO4B OO, 4 4, » oo B20) 444 056 5200 dU 080 6 » oy «= 4201 464 119 | 402 038 U29 8 ” ” 4:10 | 4:96 O48 356 0-40 0:30 | ld ,, ’ 5 3°85: 5:03 0°58 | 3:74 035 0:36 | Vaudin vives the following figures (Table XXNIII.) as showing the composition of colostrum : — TABLE XXXIIJ.—Composirion oF CoLosTRUM. | Date. Fut. Sugar. Proteivs. am aoe Percent. Percent. Percent Percent. Per cent. Evening before calving, 1-30 1:52 23-70 0-62 0-47 6°32 217 1491 0-63 0-46 ' Immediately after | 3-84 2:37 20:10 0-66 0-39 j calving (4 cows), | 1:36 1-02 19-02 0-61 0-46 : 2-42 2-56 17-68 OST 0-34 Five days after calving, d18 4:07 435 0:38 0-49 164 NORMAL MILK: ITS ADULTERATIONS, ETC. Colostrum differs from milk in containing less sugar, a fat which is very poor in volatile acids, and a high amount of nitro- genous compounds, which differ from those of milk. The dis- crepancy between the results of Engling and Houdet is due to the methods for the separation of the nitrogenous compounds not being known. Steinegger has shown that colostrum has a high aldehyde figure. Milk containing colostrum is not used for dairy purposes; at least four days should be allowed to elapse after parturition before the milk is employed for consumption. Miss E. G. Cook has, however, patented its use for the manufacture of milk for infants. Generally speaking, the milk of newly-calved cows is poorer in fat than that of cows towards the end of their period of lacta- tion. Kuhn’s experiments have shown that the casein also increases as the period of lactation advances, while the milk- sugar decreases; the mineral matter also increases towards the end of lactation. Most of the analyses on p. 154 which show a high percentage of proteins were obtained from cows which were getting dry. The milk of cows in ill-health may have a very abnormal composition. Wynter Blyth has collated the information con- cerning these in his Foods, their Composition and Analysis (q. v.). They are, however, of interest from a pathological point of view, rather than of practical importance in dairying. Limits and Standards of Milk.—The President of the Board of Agriculture and Fisheries has laid down, after enquiry had been made by a Departmental Committee on Milk Standards appointed by him, the limits of 3°0 per cent. of fat and 8°5 per cent. of solids not fat; a presumption is raised, till the contrary is proved, that any milk yielding figures on analysis below these limits is not genuine, but has in the former case been deprived of a portion of its cream, and in the latter has been adulterated by water. The figures are identical with the limits previously adopted, unofficially, by the Society of Public Analysts; in practice the official adoption of the figures has resulted in a strengthening of the limits; the wording of Clause 4 of the Sale of Food and Drugs Act, 1899, has transferred the onus of proof from the prosecution to the defence. These limits do not represent the absolute minima yet found, as will be readily seen by referring to the figures previously quoted, but are limits below which mixed milk of a herd of cows may be reasonably expected not to fall. Vieth, in discussing the question how far they could be applied to all milks, has written: ‘‘ My object is by no means LIMITS AND STANDARDS. 165 to raise the cry that the standard adopted by the Society is too high; on the contrary; I think it is very judiciously fixed, but, in upholding the standard of purity, it should not be for- gotten that the cows have never been asked for, nor have given their assent to it, and that they will at times produce milk below standard. A bad season for hay-making is, in my experience, almost invariably followed by. a particularly low depression in the quality of the milk towards the end of the winter. Should the winter be of unusual severity and length, the depression will be still more marked. Long spells of cold and wet, as well as of heat and drought, during the time when cows are kept on pasture, also unfavourably influence the quality and, I may add, quantity of milk.” Table XXXIV. will show the probable number of samples per 100,000 examined which may be expected to be found between the percentages named. TABLE XXXIV.—PERcENTAGE oF Far anp SoLips Not Fat IN MixeD MILK. | Percentage of Fat. | ace — ae ' ieee \ | \ 2-9 to 3-0 370 | S-+4 to 35 1892 DEB > 220) 209 8:3 4, St 242) 28 87 $2. 5, 8:3 | 27 2-45 2:7 37 Sl ,, $2 22 1 255 55 20 | 16 8-0 4, S1 | 8 Below 2-5 13 Below 8-0 2 | Table XXXV., p. 166, shows the percentage of samples which have fallen below the Government Standard for fat in morning milk during May and June since 1900; it is practically only in these months that any serious number of low samples occurs. In an extended series of analyses of milk, the author has found that the number of samples yielding any given percentage of fat is in agreement with that calculated by the usual methods from the theory of probabilities, provided that morning and evening milks are treated as separate series. This shows that standards can be calculated by actuarial methods from the actual results. By a formula based on the theory of probabilities, the author has calculated standards for each month below which milk should not reasonably be expected to fall for both fat and solids not fat, and in the case of fat has confirmed them by taking the 166 NORMAL MILK: ITS ADULTERATIONS, ETC. TABLE XXXV.—Fat ry Morninc MILK ONLY. May. June. 2-9to8-0}2-8to2-9]2-7to2's| BOW Jo-9t03-02-8t02-92-7to2-8| Below 1900, 4-1 0-9 0-4 a 3-0 2-0 0-4 0-2 1901, 40 2) 1:6 0-4 2-0 1-4 oe 0-4 1902, 22 2-0 0-8 am 4-7 15 0-4 se 1903, 2) 0-9 oo ie 17 0-6 0-8 . 1904, ‘ 27 1:8 0-9 0-5 Pile 4) 3-2 0-8 0-2 1905, ; 6-0 2-0 0-6 0-2 onl 2-0 0-2 8 1906, 3-0 0:8 0-4 0-2 5S 1-7 0-2 i 1907, 3-2 2-0 0-2 0-7 5°7 va U 10 0°8 1908, 0-6 0-5 0.2 4 23 0-4 0:2 ee 1909, 3-9 1-6 0-9 ae 5-2 17 0-8 01 1910, 3:0 2-1 0-8 0-5 3-0 12 10 O1 1911, 4+] 2+] 0-5 0-2 56 05 05 02 1912, 46 42 16 04 3°9 0-9 O7 ; OS 1913, 35 bap 10 13 | 46 22 06 | 10 Mean, 37 |! 18 | O7 | O83 39 | 15 | 05 0-2 mean lowest percentage of fat in the milk sent out by the Ayles- bury Dairy Company. These are :— TABLE XXXVI. Calculated Standard. | Lowest, — | Percentage of Month, | Fat in Milk i Solids not Fat. Fat. sent out. January, . r : de5 8-50 3°14 3°35 February, . 3 , 8-50 3-08 3°25 March, . " F ei 8-49 3°08 3°25 April, F ‘ F s 8-53 3°05 3-22 May, : : : oof 8-60 2°84 2-97 June, : ‘ F ‘ Sis 2°84 2°04 July, > ‘ ‘ 8:36 3-01 3-05 August, . : : . 8-28 3°09 3-08 September, : z , 8-36 ' 3°16 3-22 October, . . " z 8-52 317 S27 November, Z ‘i 5 8-49 3-13 3°22 December, A e : 8-52 3-12 3°28 According to the author's experience the limits of 30 per cent. for fat is certainly reasonable for the mixed milk of a whole _LIMITS AND STANDARDS. 167 herd, except perhaps in May and June; such milk very rarely, if ever, falls appreciably below this limit. It is far more frequent, especially during July, August, and September, for milk to contain less than 8°5 per cent. of solids not fat; in the majority of these cases, the author has found that at least 0°50 per cent. of total nitrogen and 0°70 per cent. of ash was present, and this experience has received much confirmation. Smetham and some American observers have, however, found that even these limits are somewhat too high for the milk of Dutch or Holstein- Frisian cows, and the author has also found some samples which do not conform to this rule. At the present time this breed of cows does not form a majority of English milch-cattle; on farms where they are kept other breeds yielding milk of higher quality are also milked. Multiple Standard.—For all practical purposes the multiple standard of 8°5 per cent. of solids not fat, 4°5 per cent. of milk-sugar, 0°50 per cent. of total nitrogen, and 0°70 per cent. of ash may be adopted for the purpose of judging whether a milk is of genuine composition or not. The figure for the ash is, however, liable to be increased by the addition of mineral substances added to the milk; thus boric acid and borax, used as preservatives, and salt, added to mask the addition of water, would raise the ash; estimation of the boric acid, which is absent in genuine milk, or of the chlorine, which does not often exceed 0°10 per cent., will show additions of this nature. The amount of ash insoluble in hot water is also a useful figure; it amounts in milk to at least 0°50 per cent., and is very nearly equal to the total nitrogen. A milk should never be pronounced as watered on the evidence of the solids not fat alone, unless this is well below 8:0 per cent. ; a determination of the milk-sugar. total nitrogen, and ash should be made in addition; a judgment formed on the three determina- tions will be in all probability correct, and if the figures for at least two of them are above the limit, the milk is probably venuine, Variations of Fat in Milk on Standing. — The fat globules of milk have a natural tendency to rise to the surface and to thus cause an unequal distribution of fat in different portions of the milk. Table XXNXVII. will give an idea of the rate at which appre- ciable change in the composition of the milk occurs: 12 gallons of well-mixed milk were placed in a churn with a tap at the bottom at 11°25 a.m., and a measure holding 7 quarts was drawn out every half-hour till 2°25 p.m.; each of these quantities was analysed, as also the residue left in the churn (5 quarts): the milk was undisturbed throughout. 168 NORMAL MILK: ITS ADULTERATIONS, ETC. TABLE XXXVII.—Vartations In Composition oF MILK on Stanping (LARGE CHuRN). Time. Specific Gravity. | Total Solids. Fat. Solids not Fat. Per cent. Per cent. Per ceut. 11.25 a.m, 103824 12°69 3°71 8:98 11.55 ,, 10325 12°68 3°68 9-00 12.25 p.m. 1°0328 12°35 3°34 9°01 12.55 ,, 1:0331 12°13 3:10 9-03 V25 5, 1 0334 12°03 2°95 9°08 1.55 55 10334 11°97 2°90 9:07 O25. 55 10334 11 97 2°90 9-07 Residue. 10283 16°65 7:87 8:78 In another experiment two large churns, such as are used in restaurants, each holding 12 quarts, were stood side by side; every quarter of an hour 1 quart was drawn from the tap and the amount of fat in each portion was estimated (Table XX XVIII), The residue was not analysed, but undoubtedly contained a high percentage of fat. TABLE XXXVIII.—Variarions in CompostTion or MILK on SraNDInG (SMALL CuuRNs). Time, No. I. No. Il. Start. 3°72 °/, fat. 3°72 °/, fat. 15 min, 3°65 —,, 3°64, 30, 3°72, 3°65, 45, 3:45, 3°38, 60 ,, 2°95, 2°85, 75 5; 2°35, 2°76 45 90 ,, 267s, 267, 105, 263, 260 =, 120 ,, 2°64 —,, 257, 135, 254, 250, It is seen from the results of these experiments, which are typical of many, that milk left to stand remains approximately of the same composition for short periods only—not exceeding half an hour; by continually drawing off the bottom layer, samples are obtained which become poorer and poorer in fat till the upper layer of cream is reached. A similar phenomenon is observed, if the milk is dipped from the top of a counter pan, as the following experiment will show :— Three quarts of milk were placed in a pan; every half-hour VARIATIONS IN FAT ON STANDING. 169 one pint was removed by dipping from the surface; and each portion was analysed (Table XXXIX.). TABLE XXXIX.—Variations IN ComposiTioN or MILK ON STANDING (PAN). | Time. Percentage of Fat. | Start. 3°65 | 30 min 375 ; BC s, 4:40 | 90 =, 4:15 | 120 ,, 3-75 | l Residue. 2-8) Here again it is seen that the milk does not remain practically constant in composition for more than half an hour. Court of Queen’s Bench Decision.—These figures were obtained under conditions which need never occur in practice ; indeed, the decision of the Court, of Queen’s Bench in the case of Dyke v. Gower makes it necessary that they must not occur, as it has been decided that a vendor is bound to sell milk in its natural state; it is equally an offence against the law to sell milk which has been deprived of its cream by natural rising when the milk is undisturbed, and to sell that wilfully adulterated with skim milk. Practical Allowaices for Fat Variation.—It is, however, fortunately not a matter of extreme difficulty for a vendor to comply with the spirit of this judgment: for instance, in the sale of milk from a counter pan it is easy to stir the milk every half hour, or, what is preferable, before serving each customer. When milk is delivered in the streets the churn can be fitted with one of the numerous arrangements for automatically keep- ing the cream mixed; the action of these is, too, materially aided by the motion the milk receives from the movement of the cart or barrow when drawn along the streets. A steady current of about 1 foot per hour is enough to keep milk mixed, and, except in very hot weather, milk is not churned by gentle stirring. To ensure that the composition of the milk will not vary the minutest fraction perhaps demands more skill and attention than the average milk distributor possesses, but a practical compliance with the judgment mentioned above can and ought to be obtained. The author has calculated from a large number of results that the probable variation of fat in milk due to cream rising is only 0°11 per cent. 170 NORMAL MILK: ITS ADULTERATIONS, ETC. It cannot be too strongly insisted on that the calculated standards apply only to the mixed milk of a number of cows; the milk of a single cow may be below these figures to a serious extent. As this case is one which but rarely occurs—the sale of milk being almost entirely confined to the production of herds —it is not necessary to make any allowance for the greater variations of quality of the milk of individual cows. Appeal to the Cow.—In cases of doubt it is advisable to resort to what is known as “‘ appeal to the cow,” or the “ stall or byre test.” This consists in having the cow—or cows— milked in the presence of a responsible witness who can certify to the absolute genuineness of the milk, which is analysed and compared with the suspected sample. It is desirable, if possible, that the milk of the morning and evening meals should both be examined. To make the test as fair as possible, the cows should be milked by their usual milkers at the same time of day as the previous sample, and under the same conditions; the test should be carried out at as early a date as convenient, and care should be taken that the meteorological conditions are nearly alike, as a poorer milk is yielded in warm, damp weather than if it is clear and frosty. The test should not be carried out on a Sunday or Monday, or on a public holiday or its morrow, unless the previous sample was taken on a similar day, as it has been shown that the irregularity in the time of milking—which occurs on such days —affects the quantity and quality of the milk; any serious divergence from the average quantity of milk yielded may be looked upon as throwing doubt on the reliability of the test. The witnesses must be specially careful in seeing that the cows are milked out, and that nothing occurs likely to disturb the equanimity of the cows, such as undue commotion or noise. If the milk is cooled, it is the duty of the witnesses to satisfy them- selves that the refrigerator does not leak, as well as to see that all vessels into which milk is received are clean and dry. This test, if properly carried out by competent witnesses, is very reliable ; if the suspected sample were genuine, milk will be yielded of approximately the same composition at the appeal to the cow; everything, however, depends on the competency of the witnesses. Influence of Feeding and other Conditions on the Composition of Milk.—I{ the food given to the cattle is suffi- cient both in quantity and ratio of constituents no appreciable variation in the composition of the milk is found on changing the food. The author has noticed that, if the food given makes the cows scour, the milk is likely to be low in fat, and the per- centage of fat is raised by the addition of a more binding food— eg., cotton cake—to their ration. 171 INFLUENCE OF FEEDING. CLT CON MO “MUTT PAXHy 168 FUR SE-B oI-8 8L-8 6F-L NOR 19-8 GER “quy qou sprog 18-0 OL0 IL-0 8! seo | 60 FR-0 oL-0 6L0 nL GLE 10-€ ebe LO-G wk 06-6 GRE oot EGE ‘uleqyorg St-F Chr LEP LOE SEF O8-€ OO-P €E-F OFF | 7 ‘aedny eo £6-6 ed 86-6 ToT LF 06-T 80-6 “2-T | - Quy F201 LOTT 69-6 OL-IT 66-6 96-8 Yoayy | 69-01 6T-0T ‘s pI[Os [BIO], 0880-1 0080-1 FLE0-T GOEO-T LEGO-T FSE0-L | OEO-T 9180-1 1180-1 | ‘Apavas oytoady sspulddyqy | ‘yy e10g ‘IT Gan) “‘T winyg EON MOQ SL ON MOO [TL ON BOQ | SUN BOD | “EON BOD “TX WIEVL 172 NORMAL MILK: ITS ADULTERATIONS, ETC. The figures in Table XL. afford a striking illustration cf the effect of food causing scouring on the composition of milk, and show how easy is the remedy. A herd of 26 cows (Ayrshires) was turned out into a field of new grass at the end of April, and received no other food; the percentage of fat rapidly fell, and on May 7 the author saw all the cows milked, and the foregoing analyses of the milk were made. The cows were very thin, though otherwise pronounced by a leading veterinary surgeon quite healthy, and suffered from profuse diarrhcea, the motions being quite liquid, and containing much undigested food. On this day the food was changed, and the quality of the milk steadily rose till within a week the per- centage of fat was over 3°0 per cent., and remained above this figure. The only cow of the herd which had not been turned out to the new grass was No. 13, and it is seen that her milk was practically up to the standard in fat. A too highly saccharine diet is not advisable, and may cause a disturbance in the composition of the milk. The author has examined the milk of three cows which had been fed on a ration containing much sugar; apparently the sugar had fermented in their stomachs, as the cows suffered from the effects of alcohol. The analyses were :— TABLE XLI. Cow No. 1. Cow No. 2. Cow No. 3. Before, After. Before. After. Before. | After. ; | Sp. gr., » . | 1:0322 | 10243 | 1-0315 | 1-0304 | 1-0321 | 1-0284 | Total solids, . | 12-97 9-88 12-41 11-06 11:97 | 15-58 Fat, . . | 4:26 2:87 3-63 | 2-77 314 | 5:87 Sugar, . . | 5-00 2-15, 472 4-05 472 | 0-68 Protein, 2-98 | 3-67 333 | 305 | 337 | 6-28 Ash, . | 0-73 | 0-89 0-73. 0-70 O-74 | 1:04 Solids not fat, 8-71 7-01 8-78 | 8-29 883 | 971 A. C, Abrahams has found that exposure to cold winds has the effect of causing milk low in fat to be produced. It is seen that the following rules will go a long way towards preventing abnormally low fats. (i.) Do not let the cows scour. (i.) Do not give too much saccharine food. (11.) Do not expose the cows to very cold weather. ADULTERATION. 173 Adulterations of Milk.—The chief adulterations of milk are— (1) The addition of water, which is sometimes masked by the use of a solid substance which is soluble. (2) The addition of skim or separated milk, or the removal of cream. Calculation of Added Water.—Watering is detected by the depression of the solids not fat, total nitrogen, and ash; if all three are below the limits given above, the milk may be con- demned as watered. The amount of water added is best cal- culated from the solids not fat by the formula— S es = y—- Oo Water 100 85 * 100, where & = solids not fat. This formula will give the minimum percentage of water added. It is only correct if the original milk contained 85 per cent. of solids not fat. The probable amount can be calculated by using the mean figure for solids not fat 8°9, instead of 8°5, in the above formula. Another excellent method for calculating percentaye of added water is to use the sum of the degrees of specific eravity and the fat as a datum. . G+F Water = 100 — ve x 100, where @ = degrees of gravity, and F = the percentave of fat. This will likewise give a minimum figure, and the probable amount can be obtained by substituting 36 for 34:5. The latter formula has the advantage that it is applicable without correction to milk which contains an excess or deficiency of fat, while the percentage of solids not fat is affected to some extent by variations in the fat; Table NNAVIT. will make this clear. The solids not fat vary from 878 to U8, a difference of 0°30 or 3°3 per cent. of the solids not fat; the sum of the degrees of specific gravity and fat only varies from 36°11 to 36°35, a difference of O24 or O'7 per cent. of the sum. Another formula in which the percentage of water is calculated from the aldehyde figure (A) is : x 100. 2u Water = 100 — Ag these formule fail with abnormal milks, the author has 174 NORMAL MILK: ITS ADULTERATIONS, ETC. proposed the two following formule, which hold good, not only with normal milks, but with abnormal milks in addition :— 100 iO F exceeds 4. G + F— 4L exceeds 16. (S — L) S = solids not fat, L = milk-sugar, F = fat, and G = lactometer degrees. Adulterations by Cane Sugar, &c.—Sometimes substances such as cane sugar, dextrin, or other carbohydrates or glycerine are added to mask the addition of water by raising the solids not fat; these will be detected by the sweet taste, the deficiency in total nitrogen and the ash. Cane sugar, dextrin, etc., can be detected by the discrepancy between the milk-sugar estimated by polarisation and that determined by Fehling’s solution (see pp. 90 and 95). The detection and estimation of cane sugar Is siven on p. LOL. Glycerine, if added to any appreciable extent, will render the total solids sticky, and on analysing the sample the water, fat, milk-sugar, proteins, and ash will in the aggregate be seriously below 100 per cent. It can be detected, and approximately esti- mated, by evaporating 25 c.c. of milk to a pasty consistency, treating with a mixture of alcohol and ether, and following the procedure of the maceration method of analysis; the alcohol- ether extract is evaporated and the residue exhausted with a little water and this again evaporated. If glycerine be present, a residue having a sticky consistency when cold will be left ; the weight of this, less that of the ash left on ignition, will approxi- mately give the amount of glycerine. Starch has also been used; this is detected by a blue color- ation being obtained with a solution of iodine in potassium iodide (see p. 106). Rennet is occasionally added to milk, aul more especially to separated milk, with the idea that if mixed with warm milk it will cause curdling. Its presence may be inferred if the milk curdles on warming to 40° C., and the acidity is less than 25° ; the whey’ on neutralising to an acidity of 12° will cause fresh milk to curdle at 40° C., and the amount of lime in the whey does not exceed 0°06 per cent. Brains and mammary tissue are said to have been used; this is doubtful, but they would be shown at once by the large deposit obtained on centrifuging the milk. Mineral adulterants have been employed. The use of chalk, which is popularly supposed to enter into the composition of adulterated milk, is probably hypothetical, as its insolubility would defeat the object of its use. Salt is detected in the ash ADULTERATION. 175 by an increase in the chlorides above 0°10 per cent. ; an estimation of sodium should also be made, as milk does not contain more than 0°05 per cent. ; carbonate or bicarbonate of soda is also detected by the increased alkalinity of the soluble ash; this does not exceed in genuine milk an amount equal to 0°025 per cent. Na.CO.,; an amount appreciably exceeding this is due to addition of alkali. The alkalinity of the ash should be estimated by titrating with = acid, using phenolphthalein as indicator ; 1 c.c. of the acid is with this indicator equal to 0°0106 gramme of Na.CO., Other mineral additions, such as boric acid, borax, fluorides, etc., may be added as preservatives, and not to mask the addition of water; the methods of detecting these will be given later. It has been alleged that salts of ammonia have been added to raise the total nitrogen. These would be detected by rendering alkaline with magnesium carbonate, distilling the milk, and testing the distillate with Nessler’s reagent (an alkaline solution of mercuric chloride in potassium iodide). Calculation of Fat Abstracted.—The detection of adultera- tion by removal of cream can only be effected with certainty by the estimation of fat; if this falls below 3°0 per cent., a pre- sumption is raised that cream has been abstracted. From the table on p. 159 it is seen that the mean percentage of fat varies at different times of the year; a limit of 3°25 per cent. could be used from October to January with as much justification as a limit of 3-0 for the other months. The percentage of cream abstracted is calculated by the formula Cream abstracted = 100 — = x 100, where F = percentave of fat. This formula gives a minimum percentage of fat abstracted. The figure thus calculated is almost always seriously below the truth: the probable amount can be calculated by subitituting 3°74 for 3, or, better still, the monthly average figure given in Table XXX. on p. 159 for the month in which the analysis is made. If “appeal to the cow” has been made, or if the mean com- position of the milk was approximately or exactly known, the figure representing the actual composition should be substituted for 3. The colour of the fat is of some aid in judging the amount of cream abstracted; if it is very yellow, the milk is very likely yielded by Jersey cows, and a high tigure—e.y., 4—may be substituted for 3. 176 NORMAL MILK: ITS ADULTERATIONS, ETC. The colour of the milk itself is no guide, as it is frequently artificially coloured to give it an appearance of richness. Annatto was the colouring-matter chiefly used, but this is now somewhat largely replaced by coal-tar colours, especially the sodium salt of di-methyl-amino-azo-benzene sulphonic acid or methyl orange. Artificial colouring-matters generally may be detected by pre- cipitating the casein with acetic acid, washing well with water, and digesting with strong alcohol; the casein carries down the colouring-matter and gives it up to the alcohol; on evaporating this, and taking up with a little water, the colour can be detected. Annatto is unchanged by mineral acids, while many of the coal- tar colours turn pink. The following method for the detection of colouring-matters in milk is based on a scheme devised by M. Wynter Blyth :— Preliminary Tests—(1) Allow a portion of the milk to stand in a cool place till the cream rises; if the skim milk is more highly coloured than the cream the milk is artificially coloured. (2) Add a drop or two of hydrochloric acid to a little milk ; a pink colour indicates the presence of an azo colour, of which the following, among others, may occur in milk :— Aniline yellow. Amino-azo-benzene. Butter-yellow. Chrysoidine. Di-methyl-amino-azo-benzene. Acid yellow. Salts of amino-azo-benzene sulphonic acid. Methyl-orange. Salts of di-methyl-amino-azo-benzene sulphonic acid. Orange IV. Diphenylamine-yellow. Salts of di-phenylamine-azo- benzene sulphonic acid. (3) Make the milk alkaline with sodium bicarbonate, and immerse a strip of filter paper therein for at least twelve hours. A reddish-yellow stain indicates annatto. These tests may fail to show artificial colouring-matters, because (1) aniline-yellow and butter-yellow are soluble in fat, and may rise with the cream ; (2) azo-compounds are reduced in stale milk to colourless compounds; and (3) a colour such as phosphine (di-amino-phenyl-acridine usually mixed with di-amino-toluyl- acridine) or caramel has been used. It is better, therefore, to use the general method :—Take 50 c.c. (or more) of milk, make just alkaline to litmus, and evapor- ate to a paste, and thoroughly extract the fat with ether. Evapor- ate the ethereal solution, and shake up the fat with a little hot distilled water, separate the water, and evaporate to dryness in a small porcelain dish. Pure milk gives no coloured residue ; if the residue is coloured, this will be due to a reduction product of an azo colouring-matter, or to the unreduced colouring-matter. Next, extract the fat-free residue with absolute alcohol, filter the alcoholic extract, and evaporate to dryness in three or four DETECTION OF BLOOD. 177 porcelain dishes. Unreduced colouring-matters will leave a coloured residue. A pink colour is usually due to the presence of blood; this may be detected by warming the milk to 50° C., and separating it in a high speed centrifuge (Fig. 15); if blood is present a bright red deposit is seen at the bottom of the tube. The deposit may be examined microscopically, and it is usually found that the blood-corpuscles have become considerably disintegrated, ‘| | | | | | Fig. 15.—High-Speed Centrifuge. and have the appearance shown in the plate (Fig. 16). As a confirmatory test the residue should be treated with a drop of ‘acetic acid on a microscope slide, a cover glass placed over the mixture, and the acetic acid gently evaporated over a very small flame. When nearly dry, the slide should be examined with }-inch power, and the presence of brown rhomboid crystals of heemin hydrochloride will indicate blood. Preservatives.— In order to check the growth of micro- 12 178 NORMAL MILK: ITS ADULTERATIONS, ETC. organisms in milk, and thus make it keep for a longer time than it otherwise would, preservatives are frequently added. The most common additions for this purpose are boric acid and its sodium salt, borax; salicylic acid, either alone or mixed with borax and boric acid, and sometimes in alcohol or glycerol solution ; fluorides, such as sodium fluoride or potassium acid fluoride ; fluosilicates and fluoborates; #-naphthol and salts of the 6-naphthol-sulphonic acids (abrastol), formaldehyde, and benzoic acid. Potassium nitrate has also been recommended, but it is a comparatively weak antiseptic, and is little, if at all, used. Hydrogen peroxide is also used. Fig. 16.—Blocd in Milk. Effect of Preservatives.—The effect of boric acid preser- vative and formaldehyde has been studied by the author and Harrison; taking milk which just curdles on boiling as the limit of fresh milk, the following are the extra times that the preservatives will keep milk fresh :— TABLE XLII. Borie Acid. Formaldehyde. Temperature. - aay fi pa | 0°05 0-10 0°0025 0°005 0010 | | | per cent, per cent, per cent. per cent. per cent. | | ‘ | : 60° F., 26 hours. | 40 hours. | hours. | 35 hours. | 63 hours. , | 70° B, é il4 so, i a. ET a er. 8 . 6 5 BC Eas 21 8 iy 2 Dy 45; IB) 45) 84 90° F., >| Ose TS ap ee, GE) Ge gee THE SOURING OF MILK. 179 Table XLII. shows how useless these preservatives in small amounts are, and an equal effect is produced by a few degrees lowering of temperature. The author and Miller have investigated the action of other preservatives on milk; the results at 20° C. = 68° F. were :— TABLE XLIII. 2 per cent. | 0-1 per cent. 0°05 per cent. | 0°025 per cent. Sodium benzoate, 16:7 hours. | 8-9 hours 4-1 hours, | 1:3 hours Potassium _,, 156 0 5, Ody 39 4, +| 10 ~=«4, 8-naphthol, 56°0 ” 1 90 ” 2°5 ” 0:8 ” Salicylic acid, 215 ~—C, 155 a, 70s, 42s, Sodium sulphite, 15:5 ,, 55 4, [-O5 4 —20 ,, Potassium meta- ; bisulphite, 1340 a, | 430, 21°0 55 55, O74 0°10 08s 0 044 : (ug? per cent. per cent. per cent. per cent. | per cent en ‘ “ | Boric acid, | 30-5 hours. | 20-5 hours. 17-5 hours. | 8 hours. 3-5 hours. The following substances had no appreciable preservative effect :—Sodium fluoride, potassium acid fluoride, resorcinol, phloroglucinol, phthalic acid, abrastol, sodium -naphthol- sulphonate, and cyllin. The Souring of Milk.—Lactic acid is developed by the action of micro-organisms on the milk-sugar, and the acidity of the milk is a rough measure of this. TABLE XLIV.—TeEemperature IN DEGREES FAHRENHEIT. Time in Hours, Gus 709 : soe gor 10, ' 00 1 25 15, 3 O-1 02 ' 25 210 20, 0-2 hl, 102 | 6590 25, 03 40 | 410 + 760 | 30, bl 102 = 650810 " 35, 3-0 27:0 «| 730 | 850 40, 6-0 500 =| 78-0 88-5 | 45, 10-2 650 | Slu | O15 | 50, 20-0 710 | 835 | O40 55, 35:0 750 860 «950 60, 50°0 780 885 | 96-0 70; 6% 3 680 820 | 930 970 | | 80, | 73-0 85°5 95°0 930 | 90, 73-0 88-5 | 97:0 935 | | 10u, | 800 915 | 98-0 99-0 180 NORMAL MILK: ITS ADULTERATIONS, ETC. Table XLIV. gives the average amount of acidity above the normal acidity of milk developed in the times stated at various temperatures (see also Fig. 14, p. 135). The rate of souring increases 1°5 times for a rise of 10° F. in temperature, or 2075 times for a rise of 10° C. When milk reaches an acidity of 13° above the normal it curdles on boiling, and at 65° it curdles spontaneously; the times taken to reach these points are :— Time in Hours at Acidity. €0° F. 70° F. 80° F. 90° F. 13°, - . : 47 31 21 14 65°, : : 68 44 30 20 1t is seen that lowering of temperature has an immense influ- ence on the life of milk. Boric acid preservatives are used in quantities varying from 0°01 up to 0°3 per cent. The following figures show the amounts used :— Up to 0-03 % in45 % of samples containing boric preservative. From 0-03 to 0:06 ,, 27:5 5 5 re Above O06 ,, 276 sg a In the bulk of the samples the quantity added was insufficient to have any really useful effect in hot weather. Formaldehyde appears to be added in proportions varying from 0°002 to 0°005 per cent., and only the larger quantities would be really efficient as preservatives. To sum up, it appears that to be of any real use in hot weather at least O°l per cent. of boric preservative, or 0°004 per cent. of formaldehyde is necessary, and even then the effect is only equal to that produced by cooling down the milk about 10° F.; the cost of cooling is approximately the same as the cost of preserva- tives, and so far as milk is concerned, there is absolutely no justi- fication for the use of preservatives; the practice appears to be dying out. : Objections. — The practice of adding preservatives is by many considered highly reprehensible, while others are warmly in favour of this course. Evidence that any well-marked injuiious effect follows the consumption of milk containing small amounts of preservatives is not forthcoming. Wiley, as the result of an exhaustive experiment extending over many weeks, concludes that both boric acid and borax. when continuously administered in small doses for a long period, or when given in large quantities for a short period, create dis- turbances of appetite, of digestion, and of health. PRESERVATIVES. 18] In certain patients medicinal doses of boric acid give rise to transient erythematous eruptions after relatively short periods, especially in cases of kidney disease, where the drug is not rapidly eliminated in the urine. Tunnicliffe and Rosenheim conclude that neither boric acid nor borax given for twelve days in any way affect the general health or well-being of children. On the other hand, the author has found a general consensus of opinion among medical men, who are specialists in infant feeding, that the presence of boric acid or its compounds tends to cause feeding troubles in young children. Hehner, Weber, F. J. Allan, Cripps, Leffmann and Beam, Liebreich, Halliburton, Chittenden, Mayberry and Goldsmith, and Rideal and Foulerton have shown that neither boric acid nor borax have any inhibitory effect on rennet action, or on salivary, gastric, or pancreatic digestion, beyond that traceable to the acid radicle of boric acid or the alkali of borax. They have, however, none of them ventured to claim that their experiments in vitro have more than a partial bearing on the question whether boric acid is injurious or not. Salicylic acid is in rather a different category; it is a well- known drug, and, when taken in moderate quantity, has been proved to cause injurious symptoms; its use is forbidden in France as a preservative ; it has an inhibitive effect on enzymes. Wiley has found that it tends to produce slight digestive dis- turbances. Formaldehyde is of considerable activity as a chemical agent, and combines with proteins to form compounds of a different nature. It has been found by Tunnicliffe and Rosenheim that formalde- hyde, when given for fourteen days to children, diminished phosphorus and fat assimilation, and in a delicate child it had a chemically measurable deleterious effect on general assimilation combined with a slight intestinal irritant action. Wiley was oblived to stop his experiments with formaldehyde on account of the alarming symptoms produced. ‘ Rideal and Foulerton, Bliss and Novy, Pottevin, Halliburton, Freudenreich, Mayberry and Goldsmith, Loew, Wiegle and Merkel, and Cassal have experimented on the action of formalde- hyde on artificial digestions, and all find some retardation of the time of divestion. QO. and (. W. Hehner have found that small amounts of Huorides have a very considerable effect in retarding artificial digestions. To sum up, it seems that while healthy adults can take small doses of the preservatives usually employed in milk, there is evidence that young children are not unaffected. The practice 182 NORMAL MILK: ITS ADULTERATIONS, ETC. must, therefore, be considered undesirable. The author’s ex- perience has shown that in London, the use of preservatives in milk is entirely unnecessary ; no difficulty has been found, even in summer, in delivering milk to customers in a fresh condition. Cream and butter are on a slightly different footing from milk. While the last is chiefly consumed for its food value, cream and butter are chiefly taken to improve the taste of other foods, and are consumed in comparatively small quantities; being, more- over, high in price, they may be considered as luxuries, and are expected to keep for a longer time than is naturally possible. It is readily seen that, under these circumstances, there is far more to be said in favour of the use of preservatives in cream and butter, than can be said when they are added to milk. Advantages.—The advantages of using preservatives to the vendor are obvious; they enable a perishable article to be maintained in a marketable condition for a longer time than it would otherwise remain so. As change from the action of micro-organisms is not entirely stopped, the advantage to the purchaser is by no means so apparent, and there appears to be a well-founded public opinion against the use of preservatives. A Departmental Committee of the Local Government Board, appointed to consider the question of preservatives and colouring- matters in food, reported in 1901, and made the following recom- mendations :— (a) That the use of formaldehyde or formalin, or preparations thereof, in foods or drinks be absolutely prohibited, and that salicylic acid be not used in a greater proportion than 1 gramme per pint in liquid food, or 1 gramme per pound in solid food. Its presence in all cases to be declared. (6) That the use of any preservative or colouring-matter whatever in milk offered for sale in the United Kingdom be constituted an offence under the Sale of Food and Drugs Acts. (c) That the only preservative which it shall be lawful to use in cream be boric acid, or mixtures of boric acid and borax, and in amount not exceeding 0°25 per cent., expressed as boric acid. The amount of such preservative to be notified by a label upon the vessel. (d) That the only preservative permitted to be used in butter and margarine be boric acid, or mixtures of boric acid and borax, to be used in proportions not exceeding 0°5 per cent., expressed as boric acid. (e) That in the case of all dietetic preparations intended for the use of invalids or infants chemical preservatives of all kinds be prohibited. . The Local Government Board in 1906 issued a circular letter to Local Authorities drawing their attention to the report of the PRESERVATIVES. 183 Departmental Committee, and expressing the opinion that where preservatives were found prosecutions should be instituted under the Sale of Food and Drugs Acts, and suggesting 0°005 per cent. formaldehyde and 0°057 per cent. of boric acid as the points at which injury to health was caused. In an appeal case at the Clerkenwell Sessions (Nov. 18, 1907), it was held that cream containing 0°313 per cent. of boric acid was injurious to the health of children, but not injurious to the health of adults, and further that cream is a food for infants. The fact that cream containing this amount of boric acid might be injurious to invalids was held not to affect the question whether it was injurious to health. Under the Cream Regulations of the Local Government Board, the use of boric acid is permitted in cream containing over 35 per cent. of fat, provided that the quantity is notified on a label of prescribed form and size ; 0:5 per cent. of boric acid is the quantity usually declared on these labels. Detection of Preservatives. The detection and estimation of boric acid have already been described (p. 84). Some idea as to whether boric acid or borax has been added can be obtained by applying the turmeric test (1) to a solution of ash of milk in water, and (2) to a solution of the ash in dilute hydrochloric acid. If test (1) gives no reaction, while test (2) gives a strong reaction, borax has been added; if test (2) gives a reaction no stronger than that obtained by test (1), boric acid has been used; while if test (1) gives a reaction, while test (2) gives a stronger reaction, a mixture of the two is probable. These tests are far from absolute, owing to the difficulty of judging the strength of a reaction, and, further, owing to the fact that the ash of milk is usually feebly alkaline, which would cause some of the boric acid to be reckoned as borax. Occasion- ally, the ash of milk is acid, and some of the borax would then appear as boric acid. Nothing more than rough approximate results are claimed for this method. Farrington has shown that when boric acid is added to milk its acidity to phenolphthalein is four times as great as its acidity in aqueous solution; if a milk is found to have a high acidity, say 40°, and does not smell or taste sour or curdle on boiling, it is highly probable that boric acid is present. Salicylic acid may be detected in the filtrate produced by adding mercuric nitrate to milk: if much salicylic acid be present this will acquire a red colour after some time, and when shaken 184 NORMAL MILK: ITS ADULTERATIONS, ETC. with a little amyl alcohol, the colour will pass to the amyl alcohol. For the detection of benzoic and salicylic acids the milk is made alkaline with sodium carbonate and the casein precipitated by heating on a water bath with one-tenth of the volume of 10 per cent. calcium chloride solution ; after cooling, the filtrate is neutralised and the proteins removed as in Ritthausen’s method (p. 126), The filtrate from this is acidified and extracted with a mixture of ether and petroleum ether, and the solvent washed with water, and finally a small quantity of water and a drop or two of phenolphthalein added, and dilute caustic soda dropped in with constant shaking till the aqueous portion is pink. This should be removed, boiled to expel ether, and to a portion a drop of dilute ferric chloride solution is added, and a violet coloration is developed in the presence of salicylic acid, while benzoates give a buff precipitate insoluble in dilute acetic acid. To confirm the presence of salicylic acid a portion is tested with bromine water, a curdy yellowish precipitate is produced by salicylic acid, and the characteristic smell of halogen phenol derivatives developed ; another portion is evaporated to dryness with strong nitric acid, and the residue taken up with a few drops of water ; a yellow coloration is produced on adding ammonia if salicylic acid be present. These reactions are not absolutely characteristic of salicylic acid, as phenol (carbolic acid) and other hydroxy-benzene deri- vatives behave in a similar manner. Lintner gives the following test :—Boil with a few drops of 10 per cent. mercuric nitrate solution, add 2 or 3 drops of dilute sulphuric acid, and a very small quantity of 1 per cent. sodium nitrite solution, avoiding excess. A red colour indicates the presence of salicylic acid. This test will detect 1 part in 500,000. Benzoic acid gives the reactions below; if salicylic acid is present a little bromine water is added, and a turbidity or pre- cipitate will be produced ; bromine water should be added till all the salicylic acid is precipitated, and the precipitate removed by filtration. The excess of bromine should be boiled off, and the following tests applied :— (2) Add a few pieces of magnesium and hydrochloric acid till gas begins to be evolved; benzoates are reduced to benzal- dehyde, which, has a characteristic smell. (b) Evaporate a little of the solution with soda-lime, and ignite in a current of inert gas (nitrogen formed by passing air through alkaline pyrogallol serves); benzoates are reduced to benzene (characteristic smell), which may be collected in a mixture of nitric and sulphuric acids, which form nitro-benzene PRESERVATIVES. 185 {another characteristic smell); this may be converted into aniline, diazotised and condensed with S-naphthol (red colour). (c) Evaporate a little of the solution to dryness, add 2 c.c. of aniline and 0°02 gramme rosaniline hydrochloride, and boil for twenty minutes; a blue colour is produced if benzoates are present. (7) Kvaporate a little of the solution to dryness, add a little gallic acid and | c.c. sulphuric acid; if benzoates are present anthragallol is produced, which, on dilution and making alkaline, gives a red colour passing to brown. f-naphthol is best detected by taking advantage of its easy condensation with tetrazonium salts in faintly acid solution to form dark red compounds. The author and Miller test as follows:—To 1 gramme of benzidine add 4 c.c. strong HCl and about 60 or 70 c.c. of water ; keep this solution cool, and add little by little 1 gramme sodium nitrite dissolved in about 25 c.c. of water, cooling, and shaking well between cach addition. When all the nitrite has been added nearly neutralise, using phenolphthalein as indicator. To a few c.c. of milk add a little of this solution ; if 8-naphthol is present a red colour will be produced. Do not make alkaline, as milk itself vives a brownish-red in alkaline solution. As a confirmatory test, a diazotised solution of phenylhydrazine may be used, which gives a red colour in alkaline solution with B-naphthol, but no colour with milk. lf the milk is extracted with chloroform, and the chloroform heated with caustic potash for a few minutes, a deep blue colour indicates the presence of B-naphthol. Fluorides are thus detected in the ash of milk. At least 25 c.c. of milk should be taken, and the ash treated in a platinum basin with a little strong sulphuric acid. Over the top of the basin a watch-glass coated with bees’ wax, through which a few lines are scratched, is placed, and a piece of ice or some cold water is put into the concave depression. The basin is then gently warmed and the watch-glass exposed to the action of the fumes evolved for ten minutes. In the presence of fluorides it is seen that the glass has been etched, after removal of the wax. If a drop of water is placed on the wax, away from the lines scratched through it, a white film of silica will be formed on its surface if fluosilicates be present. If fluoborates be present, this drop of water will give a boric acid reaction ; in the presence of fluoborates both a fluoride and a boric acid reaction are given by the ash of the milk. O. and C. Hehner have pointed out that when there is much boric acid in relation to the fluoride present, the test for fluorides applied directly to the ash fails. The milk should be made 186 NORMAL MILK: ITS ADULTERATIONS, ETC. alkaline, ashed, and the ash dissolved in a little acid; calcium chloride is added, and the solution made alkaline with ammonia ; the precipitate is collected, burnt, and extracted with acetic acid, and the test made on the insoluble portion. Formaldehyde, which has been introduced of late years, is now frequently employed as a milk preservative. It is generally added as a 1 per cent. solution in water, which is made by diluting the 40 per cent. solution known as “ For- malin,” “ Formal,’ “ Formol,’”’ or “‘ Formine.” A very large number of reactions for this substance have been worked out. The most easily applied test is that due to Hehner, which is best carried out as follows :—The milk is diluted with an equal volume of water, and a little 91 per cent. sulphuric acid run in so that it forms a layer at the bottom. In the presence of formaldehyde a violet-blue colour appears at the junction of the two liquids, and the colour is permanent for two or three days. This test will detect, easily, 1 part of formaldehyde in 200,000 of milk. Milk, in the absence of formaldehyde, gives a slight greenish tinge at the junction of the two liquids, and on standing a brownish colour is developed, not at the junction of the two liquids, but lower down in the acid. Leonard and Smith’s test for formaldehyde consists in heating a little milk with 3 to 5 times its volume of concentrated hydro- chloric acid; a fine violet colour is produced in the presence of formaldehyde (0°0001 per cent. to O°l per cent.). The presence of a trace of ferric chloride in the hydrochloric acid is essential. These tests are not absolutely characteristic of formaldehyde, and are not given in the presence of large amounts of this body. It is a reaction of the tryptophane of the casein with formalde- hyde, and certain other aldehydes—e.y., vanillin—give similar colours. Leonard has pointed out that pure acids give no reaction, but the presence of an oxidising agent is necessary; he found that a trace of ferric chloride gave the best results; it is better to use commercial acid than a purer form, as the necessary oxidising agent is present. As a confirmatory test, some of the milk may be curdled by dilute sulphuric acid and a little Schiff’s reagent—a solution of rosaniline bleached by sulphurous acid—added to the filtrate in a test tube, which is corked and allowed to stand. In the pre- sence of an aldehyde a violet-pink colour is produced after a short time. Excess of sulphurous acid must be avoided in preparing the reagent, or the test may fail with small amounts. There are many confirmatory tests, which are best applied to the clear solution obtained by distilling the filtrate obtained by curdling the milk with sulphuric acid. Smith and Leonard have PRESERVATIVES. 187 shown that when milk containing formaldehyde is distilled, but. a small fraction can be obtained in the distillate ; it the milk be made alkaline, still less is obtained; but a very much larger proportion is obtained by distilling from an acid solution. This is due to the fact that formaldehyde condenses with the proteins of the milk; the more perfectly these are in a state of solution, the faster is the rate of combination. Combination is more rapid at high temperatures, but takes place at ordinary tem- peratures, and the total quantity added is never obtained ; after a lapse of some time—several days—the formaldehyde disappears, and can no longer be detected. If Schiff’s test is applied to the distillate, it must be rendered faintly acid beforehand with hydrochloric acid; Hehner has shown that the distillate of milk gives a faint pink colour with schiff’s reagent after some time, but this disappears on the addi- tion of a drop or two of sulphurous acid, while the colour due to the presence of formaldehyde does not. He ascribes this to oxidation, but as it is equally well prevented by a little hydro- chloric acid, it appears that this explanation is not correct ; it is probably due to traces of alkali dissolved from the glass. The following tests are a selection from the many which have been devised :— (1) To the distillate add one drop of a dilute aqueous solution of phenol, and pour in some strong sulphuric acid down the sides of the tube. In the presence of formaldehyde a bright crimson zone appears at the junction of the two liquids. This test, which is also due to Hehner, is as delicate as the test pre- viously described, and has the further advantage that it is obtained by formaldehyde solutions of all strengths. If there is more than one part of formaldehyde per 100,000 a white turbidity is obtained in the solution above the sulphuric acid, while in strong solutions a white or pinkish curdy precipitate is obtained. Many hydroxy-derivatives of benzene, such as salicylic acid, resorcinol, and pyrogallol may be substituted for phenol. Quinol, however, gives not a red colour, but an orange-yellow one. Acetaldehyde gives an orange-yellow colour with phenol and sulphuric acid. (2) Mix the distillate with strong sulphuric acid, and sprinkle a little morphine on the surface: a violet colour is produced in the presence of formaldehyde. (3) To a decigramme of diphenylamine add 2 c.c. of strong hydrochloric acid, and pour some of the distillate into the warm solution. In the presence of formaldehyde, a white turbidity or precipitate is obtained. on further warming if necessary. The precipitate on prolonged boiling turns green. This test, lke the last, is characteristic of formaldehyde, but is not of such 188 NORMAL MILK: ITS ADULTERATIONS, ETC. great delicacy as the former ones, and may not be obtained with milk containing only a small amount. (4) Heat some of the milk for thirty minutes on the water bath with a little sulphuric acid and a drop of dimethylaniline ; filter ; render alkaline with caustic soda; and boil till the smell of dimethylaniline has disappeared. Filter; moisten the filter paper with acetic acid, and sprinkle lead peroxide on it. A blue colour is developed if formaldehyde is present. (5) To the distillate add a 3 per cent. solution of aniline. Formaldehyde produces a white precipitate, which is dissolved on boiling, but is deposited again on cooling. (6) To 5c.c. of the distillate add 1°5 c.c. of a 2 per cent. solution of phenylhydrazine hydrochloride, 4 drops ferric chloride solu- tion, and 12 drops sulphuric acid. A rose or dark red colour is produced in the presence of formaldehyde. A preservative containing a nitrite in addition to formaldehyde has been put on the market; the nitrite masks the formaldehyde reactions, but Monier-Williams has pointed out that if this is destroyed by the addition of a little urea, the tests for formalde- hyde may be obtained. Hydrogen peroxide is employed as a preserving agent; Budde has patented a process which consists in adding hydrogen per- oxide to milk, and heating to 50° to 55° C. to complete the liberation of the oxygen by the catalase of milk. It appears to act by liberating oxygen in the interior of the micro-organisms present, and thus bursting them. If a milk is found to contain abundance of soluble albumin, and not to give the para-phenylene-diamine or ortol reactions {p. 195), it is probable that it has been treated by Budde’s process. Hydrogen peroxide may be detected in milk by adding to a small quantity of fresh milk a little ortol, and adding an equal bulk of the suspected milk. In the presence of hydrogen per- oxide a red colour will be produced. A preservative consisting of a solution of hydrogen peroxide in brine and pellets of potassium carbonate and citrate has been put on the market; sodium peroxide and perchlorate are also used. M. Wynter Blyth has devised the following method for deter- mining the presence of preservatives in milk :— (1) Measure 10 ¢.c. of each milk into clean wide test tubes. (2) Measure 10 c.c. of a sterile milk known to be free from preservatives into a test tube (these control tubes can be kept ready for use). (3) Add to each milk 2 c.c. of a very strong slightly alkaline solution of litmus. If any tube is not the same shade of blue PRESERVATION OF MILK SAMPLES. 189 x as the control, add very carefully a o solution of caustic soda drop by drop till the correct shade is obtained. (4) Plug all tubes with cotton wool, and heat them in a water bath kept at 80° C. for ten minutes. (5) Cool the tubes, and add to each 0°5 c.c. of a solution con- taining 0° c.c. of sour milk per 100 c.c., shake well, and let the tubes stand for twenty-four hours at a temperature between 15° C. and 24° C., or until the control tube is white. If preservatives are absent the milk will become white at the same time as the control; in the presence of preservatives the tubes will remain blue or pink. If formaldehyde is found a quantitative estimation may be made by making up a series of tubes containing known amounts of formaldehyde, and keeping these and the tubes of the milks to be tested at a temperature of 37° C.; it is also advisable to dilute the milk 10 and 100 times, prepare tubes from the diluted milk, and keep these at 22° C. The controls kept at 37° may contain 0°005, 0°003, and 0°001 per cent. formaldehyde, and those kept at 22°, 0°001, 0°0008, 0°0005, and 0°0003 per cent. By noting which of the control tubes is decolourised at the same time as the sample to be tested, a fairly accurate estimation. of the amount of formaldehyde present may be made. Preservation of Milk Samples. Where any special importance is attached to the analysis of any sample, it is an advantage to preserve the sample for refer- ence and further corroborative analysis. Preservatives are added to effect this. The following substances have been used :— Alcohol.—Allen has suggested adding to the milk to be kept twice its weight of alcohol; his experience and that of Hehner show that analytical data can be obtained on the preserved milk (making allowance for the alcohol added) which agree with the original sample. The objection to this method is that a large amount of a volatile substance is added, and a correction, the exactness of which depends on the amount of alcohol present, must be made. Milk-sugar and salts are also deposited after some time, and are difticult of complete redistribution. Chloroform.—When added in the proportion of 1 c.c. to 100 ¢.e. of milk it keeps the milk well for a short time. It has the advantage of dissolving in the fat and keeping the cream in an easily miscible condition. As Babcock and Russell have shown, it does not stop enzymic action; hence changes in the proteins. due to this cause, proceed as if no chloroform had been. 190 NORMAL MILK: ITS ADULTERATIONS, ETC. added. The correction to be applied is small. For keeping samples for a short period, say ten days, this method is good. Ether.—This preservative is nearly as good as chloroform ; it is, however, not quite so good a preservative and is more volatile. Collins recommends a mixture of ether and chloroform of specific gravity 1°032, as it does not affect the specific gravity of the milk. The author has, however, shown that ether and chloroform keep the fat in a liquid condition, and that the specific gravity is lowered by this cause. The estimation of the fat by the Gerber method is too high in the presence of chloroform. Terpenes, Thymol, Dichlorophenol, and Salicylic Acid.— These keep the milk, but allow the cream to rise to the surface, where it sets in a firm layer and is not easily redistributed. Hydrofluoric Acid and Fluoboric Acid.—The author has proved that these substances, when added to fresh samples in the proportion of 4 c.c. to 100 c.c. of milk, keep them in good condition, and, after a year, analysis gives the same figures as those previously found. They curdle the milk, however, so that the sample must be well shaken to bring the precipitated casein into a fine state of division; a little of the bottle is dissolved and the ash is thereby slightly increased. The author has found this method to be one of the best. Formalin.—The addition of formalin has many advantages. A very minute amount of the 40 per cent. solution need be added (2 drops per 100 ¢.c.), and no correction is necessary for so small a quantity. Siegfeld finds that the presence of much formaldehyde in milk has a tendency to increase the amount of fat by the Gerber method. This may be obviated by adding 1 ¢.c. of hydrogen peroxide, or better, 0°5 of a 40 per cent. solution of hydroxyl- amine hydrochloride per 100 ¢.c. of milk, and correcting for increase of volume. The formaldehyde, however, combines with the protein, and raises the apparent percentage of total solids and solids not fat. Bevan has also suggested that the milk-sugar is hydrolysed into dextrose and galactose, as he found the increase in total solids more than the total amount of formaldehyde added; but this has been disproved by Hoft. Potassium Bichromate, Mercuric Chloride, and Solid Anutiseptics.—These add considerably to the weight of the total solids and solids not fat, and cannot, therefore, be recom: mended. If fat only is to be determined they are efficient. Siegfeld does not consider that the analysis of samples preserved by potassium bichromate is trustworthy. Sterilisation may be resorted to. Certain changes take place, THE ACTION OF HEAT ON MILK. 191 which do not usually interfere with the analysis. The cream rises and clots on the surface, and it is not easy to obtain an average sample. Cold Storage.—Samples may be frozen and kept in a cold chamber, if one is available; they keep for an indefinite period thus, but require carefully remelting and remixing. This method, which is not always available, is superior to all others, and should be resorted to in those dairies which possess a freezing plant and cold storage room. The Action of Heat on Milk.—When milk is heated the following changes occur :—At about 70° C. a change takes place in the albumin; it is not precipitated, but is converted into a form which is precipitated by acids, magnesium sulphate, and other precipitants of casein. At about 80° C. certain organised principles, the nature of which is not fully known, undergo a change. The presence of these principles in an unchanged form is shown by the following reactions :—They cause an evolution of gas from hydrogen per- oxide in the cold and give a blue colour with para-phenylene- diamine (para-di-amino-benzene), and hydrogen peroxide. Other substances may be substituted for the para-phenylene-diamine, but, according to Lefimann, this substance is the most charac- teristic. Rosier, working in the author’s laboratory, has found that meta-phenylene-diamine gives very characteristic results, if a small quantity of amyl alcohol is added to dissolve and concentrate the light blue colouring-matter formed. Saul re- commends ‘“‘ortol,’”’ which is a mixture of quinol with ortho- methyl-amino-phenol. Near 100° C. calcium salts in small amount are deposited, and, by keeping at this temperature for some time, slight oxidation sets in, with the production of traces of formic acid and a marked reduction of the rotatory power of the milk-sugar; a brown colour is produced at the same time. A deposition of salts, and perhaps, also of albumin takes place on the fat globules, which increases their mean density, causing them to rise slowly to the surface, when the milk is afterwards cooled; during the heating the fat globules are expanded and may somewhat coalesce. If the surface of the milk is freely exposed to the air, a skin forms at temperatures exceeding 60° C. This has been stated to consist of casein, but has not the properties of this substance ; it is partly of a protein character, and there is some reason to suppose that it is an oxidation product. It contains all the con- stituents of the milk in a concentrated form. The taste and smell of milk are changed by heating to above 70° C. It is not known how far the action of heat on milk affects its digestive qualities. Milk which has been heated is curdled less 192 NORMAL MILK: ITS ADULTERATIONS, ETC. readily by rennet than fresh milk, but there are good grounds for the view that this is due to a change in the distribution of the calcium salts as well as possibly to a change in the casein. It has been claimed that sterilised or boiled milk is more easy of digestion than unboiled milk, but this, again, is possibly due to the fact that it is not curdled so easily in the stomach, and does not produce so firm a clot. There appears to be no evidence that healthy adults digest boiled milk either more or less readily than unboiled milk. In one respect boiled milk is less to be preferred than fresh milk. From the evidence adduced by Barlow, and since fully confirmed, it seems that children fed exclusively on sterilised milk have a scorbutic tendency. It has long been known that the absence of fresh food of any descrip- tion is a predisposing cause of scurvy, but no substance has yet been identified as the agent which confers anti-scorbutic pro- perties. It is of considerable importance to be able to distinguish between fresh milk, on the one hand, and “ pasteurised’’ or * sterilised ’’ milk, on the other. Sterilised Milk. Milk is a product which affords all the necessary nourishment for the growth of micro-organisms; these not only develop products which cause alteration of the milk—e.g., lactic acid and proteolytic enzymes—but also are in some cases injurious to health. They are destroyed by heat. Hence milk is frequently “ sterilised’ by heat, the object being to bring about the de- struction of the micro-organisms. Many processes are used. Pasteur originally recommended heating to 70° C. for a short time, a process which was sufficient to destroy all adult forms of pathogenic organisms and, practi- cally, all others. The spores, however, were left untouched and retained their vitality ; on cooling to the mean air temperature these developed into the adult forms and resumed their activity. To destroy the spores, a process of continued “ pasteurisation ” has been used. This consists of alternately heating to 70° C. for, say, twenty minutes; cooling to a lower temperature and keeping at this temperature for a sufficient length of time to allow the spores to develop ; again heating to 70°; and repeating this process many times. By this process, which is very tedious, the taste and composition of the milk undergoes but little alter- ation. It has been found that most spores can be killed by continued STERILISED MILK. 193 exposure at higher temperatures. The temperature of boiling water is one much used, as it can be easily attained, but higher temperatures are sometimes resorted to by heating the milk under pressure; the higher the temperature, the shorter the time necessary to kill all microbial life. Another method adopted is to alternate successive short periods of heating to high temperatures with intervals during which the milk is kept at the ordinary temperature. Numerous modifications of these methods have formed the subjects of patents. Analytical Characters.—As, practically, no milk sterilised by successive heating to a temperature not exceeding 70” C, is sold commercially, it will be sufficient to describe the methods. for characterising milk which has been heated above the coagu- lating point of albumin. The most marked characteristic distinguishing sterilised milk from new milk is the state in which the albumin exists. As previously stated, it is probable that albumin exists in milk in combination with a base; on heating milk, no coagulation of albumin takes place, but on acidifying, or saturating with mag- nesium sulphate, the albumin separates with the casein. The albumin appears to be changed from a soluble to a colloidal form. (Not more than 0-1 per cent. of albumin is found in steri- lised milk in the soluble form.) The casein separates on acidi- fying in a more finely divided state. If the milk has been heated to 100° C. or a higher temperature for any length of time, the rotatory power of the milk-sugar undergoes a serious reduction, the cupric reducing power not changing to any appreciable extent. The milk also assumes a slight brownish colour, due probably to the formation of a “caramelised ” body of low rotatory power. The cream rises with extreme slowness; in three hours, prac- tically no cream is observed on the surface of the milk; and after six hours, the layer is only about one-tenth of that given by new milk. If sterilised milk be allowed to stand for twenty- four hours or more the bulk of the cream will rise to the surface, but the quantity will be less than that yielded by new milk: the cream will, however, contain a distinctly larger percentaye of fat, about 40 per cent., as against less than 30 per cent. in the cream yielded by new milk. The diminished yield of cream is a property shared also by milk which has been pasteurised by heating to about 70°, but the rate of rise of cream in pasteurised milk is fairly rapid ; practically the same amounts are found in three hours as in six hours. The total quantity of cream from pasteurised milk is about half that of fresh milk. The following figures, which, together with those in Table 194 NORMAL MILK: ITS ADULTERATIONS, ETC. XLIX., were obtained by Boseley and the author (Tables XLV., XLVI., XLVII.), will illustrate the above facts :— TABLE XLV.—ComposiTIon oF STERILISED MILK. Sterilised Milk allowed to stand for Six Hours. No. Fat in Milk. Cream. Fat in Cream. | Fat in Skim Milk. Per cent. Per cent. Per cent. Per cent. 1 4°30 1:3 23:°3 4:05 2 3°80 0: 22°3 3°67 3 £25 18 20°6 3°95 4 4:10 19 24°7 3°70 5 5°35 2°8 31°4 4°60 6 3°62 0:3 ve ete & TABLE XLVI.—Composition oF STERILISED MILK. Sterilised Milk allowed to stand for Twenty-four Hours. No. Fat in Milk. Cream. Fat in Cream. | Fat in Skim Milk. Per cent. Per cent. Per cent. Per cent. 1 " 70 46'8 1:10 2 3°80 6-0 418 1:37 3 4°25 8:8 39°0 0 90 4 4:10 87 41:0 0°58 5 5°36 ll-t 41-4 0°85 6 3°62 0-8 sis 3°48 TABLE XLVII.—Composition or New MILK. New Milk allowed to stand for Six Hours. No. Fat in Milk. Cream. Fat in Cream. | Fat in Skim Milk. Per cent. Per cent. Per cent. Per cent. 1 4:05 9:2 17°4 2°70 2 4:20 11:2 16°5 2°65 3 3°90 9°8 159 i 2°60 4 3°70 9°8 18-0 2°15 5 4°45 135 16°8 2°30 Table XLVII. showing the behaviour of new milk is produced here for the sake of comparison. The samples 1 to 5 are from the same cows which respectively yielded the samples with corresponding numbers in the tables illustrating the behaviour of sterilised milk. DETECTION OF STERILISED MILK. 195 Condensed unsweetened milk, which has been diluted to the original volume with water, has all the analytical characteristics of sterilised milk. It throws up its cream rather less readily even than sterilised milk. No. 6 in Tables XLY. and XLVI. was diluted condensed milk. This is in no way due to the fact that it has been condensed, but is owing to the sterilising process that it has undergone. There appears to be no good method of dis- criminating between condensed milk diluted with water and sterilised milk. If a water containing large amounts of nitrates has been used for diluting the condensed milk, a strong diphenyl- amine reaction will indicate the probability that water has been added ; this test is not of a sufficiently absolute character to be relied on. This is to be regretted. The subject has been con- sidered of sufficient importance by the British Dairy Farmers’ Association to induce them to offer a gold medal for the discovery of such a method. Detection of Sterilised Milk in New Milk.—To distinguish new milk on the one hand from milk which has been sterilised on the other, the following methods may be employed :— (1) Place 100 c.c. of milk in a graduated cylinder (or fill a ‘creamometer’’) and allow it to stand for six hours at a tem- perature of 60° F, (155° C.); note the percentage of cream. If less than 2°5 per cent. of cream for each | per cent. of fat in the milk has risen to the surface, the milk may be considered suspi- cious. If the quantity of cream falls markedly below 2 per cent. for each 1 per cent. of fat, it is highly probable that sterilised milk 1s present. (2) Estimate the albumin by the method of Hoppe-Seyler or, better, that of Sebelein. If less than 0°35 per cent. is found, sterilised milk may be considered to be present. (3) Estimate the milk-sugar by the polariscope, and also gravimetrically in duplicate; if the difference between the two estimations be more than O-2 per cent., it will be corroborative evidence of the presence of sterilised milk. (4) To about 5 c.c. of milk add as much powdered para- phenylene-diamine as will lie on the point of a knife, and shake well; on the addition of a drop or two of a 10-volume solution of hydrogen peroxide fresh milk gives a blue coloration; “ pas- teurised ” milk gives a similar reaction, not, however, so marked ; while ** sterilised ’ milk cives no coloration within ten minutes. A mixture of * sterilised ’’ and fresh milk will give the characters of * pasteurised ”” milk. The hydrochloride of meta-phenylene-diamine may be sub- stituted with advantage for the para-compound. The coloration is paler, and not quite so quickly developed. By shaking with an equal volume of amy] alcohol the blue substance is dissolved in ‘ 196 NORMAL MILK: ITS ADULTERATIONS, ETC. the alcohol layer, and the test is thus rendered more reliable in the presence of substances which modify the tint (e.g., formaldehyde). Other substances, such as quinol or tincture of guaiacum, may be used ; of these the one recommended by Saul, and found most effective by the author, is “ ortol,”’ which is sold as a photographic developer. This gives a fine red colour with unboiled milk. These tests show that the milk has been heated above 80° C., as the “ peroxydase ” which gives rise to the reactions is destroyed at this temperature. If the milk has been heated with hydrogen peroxide, the tests with phenylene-diamine or ortol will fail, as the peroxydase is also destroyed if an excess of hydrogen peroxide is added to milk. Another test is to add a solution of methylene blue containing formaldehyde and keep the milk out of contact with air; fresh milk decolourises this, and boiled milk does not. This test appears not to depend on any constituent of the milk, but on the presence of enzymes (reductases) secreted by micro-organisms. Milk treated with hydrogen peroxide gives this test. The rate at which methylene blue is decolourised is a rough index of bacterial contamination. A cultivated palate may also detect a boiled taste; this will certainly be noticed with “ sterilised”? milk. It is doubtful whether a proportion of sterilised milk much below 30 per cent. could be detected with certainty when mixed with new milk. The proportion of sterilised milk should be deduced from the percentage of soluble albumin by the following formula :— 0-4 — percentage of soluble albumin Percentage of sterilised milk = 0-4 *« 100. This is based on the supposition that new milk contains 0°4 per cent. of albumin, while in sterilised milk the albumin has been removed. The estimation of albumin is the most reliable test. There are many causes which influence the rising of cream, such as the temperature to which the milk has been warmed or cooled ; the size of the fat globules, which varies with the stage of lacta- tion; and the acidity of the milk. The milk may also have been “homogenised” by the fat globules having been broken up, in which case practically no cream will rise. No quantitative deductions can be drawn from observations of the rate of the rising of cream. The fall in specific rotatory power of milk-sugar is by no means constant, as milks sterilised side by side may show very appreciable variations in this respect. Tests other than the estimation of albumin must be considered as merely corroborative and of qualitative value only. DETECTION OF STERILISED MILK. 197 It must be remembered, however, that no sharp distinction can be drawn between milk which has been raised to a tempera- ture over 70° C, for a short period, and which is naturally not sterilised in the true sense of the term, and the milk which has been heated for a sufficient length of time to destroy all microbial life. For this reason, a milk should not be reported as sterilised, solely on the result of a very low percentage of albumin, if neither the “‘ creamometer ” nor the para-phenylene-diamine nor “ milk- sugar” tests give corroborative indications. It is probable that the milk, in this case, has been pasteurised slightly above 70° C. The following figures (Table XLVIII.) by C. H. Stewart show the percentage of albumin found in milk raised to various tem- peratures :— TABLE XLVIIL—Percenrace or ALBUMIN IN MILK AT Various TEMPERATURES. | ’ yiaivae . Soluble Albumin in| Soluble Albumin in PUNE OF MEaUINes Fresh Milk. Heated Milk. 10 minutes at 60°C., \ | { | are | 30 oy ent hee . 10 yg es PES lo ” ” TWC., ° a os 10 nor ape ON ess 0-070 [ 0 sae a KS F 0-050 | 10 * iy BOCES. none 3U ai gee! bgt . none The following analyses (Table XLIX.) will show to what extent the methods above described can be depended on :— TABLE NLIX.—Comparative ANALYSES oF MixepD FREsH AND STERILISED MILKs. ; ' | as Percentage Sterilised. | | a). 2 le... ~ ee ge || ee 2 2 S| B24 e = + 3 i “4 x o a =a | a a i << en ar (hie be ee Be tl! ae (oes Pp. Gp Pete p. CG pe pee i | a 1 3860 72] P87 080 F853 465 | 38 | 29 | 25 2 40 we ¢ Oat O84 479 46S Genuine ; 3. 8H0 75 ) bo 1029 479 4-64 | ee Be 25 1 o70 438 Lie lolé 493 40) 1 56 G1 3 60 fo So CC SD tad UL 30% 8h | Aa 6 fou ri }ss) 027 sus ; 82 gf Be 79 Zl 035 ; Genumne | i 198 NORMAL MILK: ITS ADULTERATIONS, ETC. Condensed Milk. For convenience of transport, milk is deprived of the bulk of its water by evaporation under diminished pressure in a vacuum apparatus fitted with a condenser, or by heating to a low tempera- ture and exposing a large surface to evaporation; this is termed condensed or evaporated milk. It is made in two forms: sweetened condensed milk, which is a preparation of milk and cane sugar; and unsweetened condensed milk, which consists of milk evaporated per se. The methods of manufacture are similar. In the manufacture of sweetened condensed milk 11 lbs. of cane sugar are added to each gallon of milk, and the mixture heated to such a tempera- ture that it will commence to boil at once on being admitted te the vacuum pan. It is allowed to flow in slowly, the pump being kept working the whole time, and no heat is applied till all the milk is in the pan. By this procedure the gases of the milk are drawn out, and on applying heat the milk boils without frothing over. By carefully regulating the supply of heat to the pan, and cold water to the condenser, the milk can be boiled at an even rapid rate till sufficiently concentrated, a point which can be easily told by an experienced operator. The whole oper- ation is controlled by looking through a glass sight-hole let into the upper portion of the pan. The finished product has a density of about 1:28 and weighs one-third of the original milk; it only occupies three-elevenths of the original volume—i.e., 1 gallon of milk is evaporated to 24 pints. Commercial glucose is sometimes substituted for a part or the whole of the cane sugar. Machines employing heated discs or rollers which d:p into the milk, and carry up thin layers on being rotated, or in which the milk is exposed in shallow trays, are also used to condense milk. Milk may be also concentrated by freezing and removing the ice deposited. Composition of Sweetened Milk.—The following analyses (Table L.) will show the composition of sweetened condensed milks. The first three are condensed whole milks—i.c., the milk has been evaporated without previous removal of the cream; the last four are condensed separated milk, the separated milk having been mixed with cane sugar and evaporated. These milks are not usually sterilised, as the large amount of dissolved matter and the small amount of water renders them unsuitable for the development of micro-organisms; they keep for a long time without appreciable change. CONDENSED MILK. 199 TABLE L.—Composirion or SWEETENED MILK, Authority. Water. | Fat. ee ee Protein.} Ash. | Total. Per ct. | Per ct. | Per ct. | Perct. | Perct. | Perct. | Per ct. Author, - » «| 24:06 | 11-28 | 13-97 | 38 31 9°36 | 2°13 99°11 Pearmain & Moor, | 26:10 | 10°84 | 14-68 | 36-93*| 9°55 | 1-90 | 100-00 I leischmann, i 25°69 | 10°98 | 16:29 | 32°37 | 12°33 | 2°34 | lon-n9 Pearmain & Moor, , 29°87 1:17 | 14°68 | 41°54*| 10°74 | 2-00 | 100-00 Author, . . 29°05 1:28 | 14:91 | 40-07 | 10°63 | 2°33 | 98-27 - : . | 29-23 0°64 | 15°50 | 40°19 | 10°73 | 2°63 95°92 vi » «| 28°43 0°36 | 16°88 | 39-27 | 11°73 | 2-58 We) * By difference. Composition of Unsweetened Milk.—Unsweetened con- densed milks are prepared in a similar manner, except that the addition of sugar is omitted. The composition of this product is shown by the following analyses (Table LI.) :— TABLE Ll.—Composirion or UxsweeteNep MILK. . | Authority. Water. Fat. Mike | Susur. Protein. Ash. | Total. Per cent, | Per cent. | Per cent. | Per cent. Per cent.) Per cent. Author,. . . .] 6347 10 22 1298 | 1030) 2-07 904, 99 eos ow | GRO 11°91 13-04 9°68 21d OUT as ; 2} GBT | 1086 | 13°38 9°80 2-21 99°32 Pearmain & Moor, | 61°96 10°67 15°50 9:57 2-30 | 100-00 Aschmann,. . . | 69°35 9:23 10°98 9-41 1°63 | 100°00 These milks have all been sterilised by heat. They have the analytical characters of sterilised milk. Unsterilised condensed milk is also an article of commerce ; Pearmain and Moor haye found boric acid in a preparation of this kind. which was sold for diluting and mixing with whole milk. It is noticed that the totals of analyses of condensed milk almost invariably add up distinctly below 100 per cent.; it is probable that the milk-sugar is underestimated. In condensed milk the layer of solution which is attracted round the fat globules by surface energy has probably a composition which is identical with the composition of the liquid in which the globules are suspended. When condensed milk is diluted with water it is doubtful whether the liquid in this layer is diluted by the water, 2.00 NORMAL MILK: ITS ADULTERATIONS, ETC. as it is held by a great force, and acts as though separated by a gemi-permeable membrane, through which the dissolved solids must pass by osmose. As the milk is usually diluted with cold water, this process of osmose takes a considerable time, and the whole of the milk-sugar is not obtained in solution, but a portion is taken down by the fat globules, when they are removed previous to the estimation of the milk-sugar. The same cause can be assigned to the fact that the fat globules in diluted condensed milk rise with such extreme slowness ; a dense layer round the globules increases its mean density, and makes this nearly approach the density of the serum. Dilution.—The directions on the label of sweetened condensed milk are often somewhat misleading. For some purposes—e.g., for infant feeding—the directions given are to dilute with five or even seven parts of water. Supposing that these dilutions are performed by volume, the composition will be as follows :-— TABLE LII. | Condensed Whole Milk. Condensed Skim Milk. With 5 With 7 With 5 With 7 Volumes of | Volumes of | Volumes of | Volumes of Water. Water. Water. Water. Fat, 7 ‘ . 2:02 1°51 0:21 0-16 Milk-sugar, . 2°57 1:93 3°20 2°40 Cane sugar, . 5 7:33 5°50 8°53 6°40 Protein, « ‘ 3 1:83 1:37 2°24 1:68 Ash, i ‘ ‘ 0°40 0:30 0:33 0°40 Compared with the average composition of human milk which is Fat, : F - 33 Protein, : oe Deb. Sugar, . is - 68 Ash, é ‘ « 0-2 we see that there is a serious deficiency of fat, especially in the diluted condensed skim milk, and a great excess of total sugar. Food Value.—Riibners has stated that as a food 2:43 parts of sugar are equal to 1 part of fat. Calculating the value of fat as sugar by this factor, we get the following values for the food value of fat and sugar :— : Condensed Whole Milk. Condensed Skim Milk. Human Milk. With 5 With 7 With 5 With 7 Volumes. Volumes. Volumes. Volumes, 14:82 14°61 10:96 12°34 9 23 Only in the case of the condensed whole milk diluted with MILK POWDERS. 207 5 volumes of water does the food value approximate to that of human milk ; it is doubtful, however, whether fat can be replaced entirely by cane sugar, especially for young infants. Milk Powders.—There are several methods of preparing milk powders; in the Just-Hatmaker process the milk is evaporated on rollers heated by high-pressure steam above the temperature of boiling water, and the dried layer of milk is continuously taken off by a knife set at a suitable angle. Other processes employ evaporation on rollers or discs heated to a lower tem- perature im vacuo, and the milk is preferably previously con- centrated in a vacuum pan to one-third of its bulk. The milk may also, after preliminary concentration, be dried in shallow trays mm vacuo, or on bands of wire gauze or other material. Another excellent method is to atomise the milk by spraying, and to evaporate this in a current of hot air. In order to ensure that the milk powder is soluble in water, a small amount of an alkali—sodium carbonate, sodium phos- phate, or saccharate of lime—is sometimes added. To prevent a separation of the fat in large particles on remixing the milk powder, the milk is often homogenised before drying; this has the further advantage that the fat has less tendency to become rancid, The table below gives the analysis of seven samples :— TABLE LUI—Comprositrion or Mitk Pownerrs. Moisture, A | 6:39 | 4:92] 3-30 | 355 $74 S15 6-03 Fat, ‘ 2 2735) 27°98 23°97 2:55 2h 190) 25-60 Milk-sugar, 31-42 | 34:16 37-32) 45-60 82-24 384-96 32-83 Cane sugar, 1:25 | 153) 2-8u ge ns a ae | 2-00 Protein, 27-48 | 24-50, 26:38 | 85-45 26-81-10 23-84 Ash, ; HOU | G2 GID) TSH 563 | F1l 6-44 Total, L OSL! 99-14 | §S-69 97-84. 98-43 | 98-22 9-74 | Water of hydra- : 165; 1:80 1-96 240) Lu Test 1:73 tion, . Total, © L029 10094 1006S 190-24 10-13 100-06 OS-47 i Change of tem- | i —0-2° ae 013° perature on!: mixing with | water, 0-2 202 NORMAL MILK: ITS ADULTERATIONS, ETC. It is noticed that none of the analyses add up to 100 per cent., but are considerably low; the milk-sugar has been calculated as anhydrous sugar, and here lies the reason for the deficiency. On shaking the solid residue obtained by drying milk on the water-bath, in which the milk-sugar certainly exists as anhydrous sugar, with water a rise of temperature always takes place; anhydrous milk-sugar mixed with water always causes a rise of temperature, whilst hydrated milk-sugar causes a fall of 0°55° if more than can be at once dissolved is added. The milk powders examined, with one exception (No. 2), all caused a fall of tem- perature, and it is seen that the addition of the water of hydration to the total gives figures which are but slightly in excess of 100 per cent.; both the change of temperature and the slight excess over 100 per cent. indicate that the bulk of the milk- sugar, though not all, exists as hydrated sugar. Sample Ne. 2 differed in appearance from the others, being a heavy powder, instead of being light and flaky, and had doubtless been more dried, and probably contains a considerable proportion of anhy- drous sugar; it is noticed that the addition of the water of hydra- tion would make the total nearly 101 per cent. Sample No. 7 gives a low total, which is probably accounted for by the presence of invert sugar. It will be noticed that samples 2, 3, 4, and 7 contain small quantities of cane sugar; this in sample 2 was admittedly added in the form of saccharate of lime, and was certainly so added, judging from the analytical figures, in No. 7. In Table LIV. the composition of the original milks, on the assumption that they contain 9:0 per cent. of solids not fat, are given :— TABLE LIV.—Composition or OrtcinaL MILks. | 1 2 3 4 | 5 | 6 7 | ! | i} Fat, 379 | 388 | 3-09 | 026 9 407 245 365 | Milk-sugar, . | 4:36 | 473 | 487 | 462 | 450 | 430 , 468 Protein, 381 | 3-41 | 340 | 358 | 3-71 | 3-82 | 3-40 | Ash, 0-83 | 0-87 | 0-80 | 0-80 | 0-79 O87 ) 0-92 CaO, O19 | O21 | O17 | O17 | O17 0-19 | O87 P,0., 0-23 | O24 | 0-23 | 0-23 | 0-23 | 0-29 | O-24 Acidity, 84° | 13-27 | 16-8? | 165° ie ° | a De From this table it is seen that No. 4 is made from separated milk, and No. 6 from milk deprived of a portion of its cream. MILK POWDERS. 205 The milk used to prepare No. 3 is only just above the Govern- ment standard. The normal percentages of lime and phosphoric anhydride in milk are 0°17 per cent. and 0°23 per cent. respectively, but vary somewhat with the protein, and the normal acidity is not far from 20°. From a consideration of the results, it would appear that Nos. 2 and 7 have received an addition of saccharate of lime; and No. 6 has received an addition of a phosphate. Nos. 3 and 4 contain cane sugar, but there is no evidence of the addition of saccharate of lime. No. 1 probably received an addition of sodium carbonate, as the lime is not high enough considering the high protein to indicate an addition of this substance, and No. 5 appears to have received no addition whatever. Milk powders containing cane sugar are also made. Two samples examined by the author had the following composition :— TABLE LY. Per cent. Per cent. lat, P 15-2 13-5 Milk-sugar, 21:7 Bibs Cane sugar, ; : 42:5 40-9 Protein, . i . dl 14-9 Ash, ‘ 3-3 BY Both had a slivhtly rancid odour and taste. When dissolved in water some of the fat was not emulsified. The Action of Cold on Milk—Composition.—When milk is exposed to a low temperature it partially freezes. Like other aqueous solutions the freezing point is below that of water, and is about — 0°55° C, (31° F.), estimated in the Beckmann apparatus. The frozen portion has not the same composition as the milk from which it was prepared, but contains a larger quantity of water. Owing to the facts that milk has not a point of maximum density, and that it does not freeze as a homogeneous substance, ice never forms in a solid layer on the surface. The following analyses (Table LVI.) will show the composition of the ice and liquid portion respectively :— 204 NORMAL MILK: ITS ADULTERATIONS, ETC. TABLE LVI.—Composirion or THE Sotip anp Ligurp Portions oF Frozen MILK. Liquid Portion. Melted Ice. Percentage of Ice Formed, 1:2 per cent. Specific gravity, . : 1:0320 10245 Per cent. Per cent. Water, 7 o 96°72 ; Fat, . : . : 4:11 2°40 Protein,. . 5 _ 3°56 2°40 Sugar, . : a . 4:87 3°05 Ash, . : F . 0°74 052 - Percentage of Ice Formed, 2 per cent. Specific gravity, . . 1:0330 1:0190 Per cent. Per cent. Water, F . . 87:10 91°83 Fat, . : P 3°87 2-56 Protein... . ‘ 3:21 2°28 Sugar, . s . ‘ 5-08 2°89 Ash, . . - A U-74 O44 Percentage of Ice Formed, 2:25 per cent. Specific gravity, . e 1-0330 10180 Per cent. Per cent. Water, F : : 87-21 92°46 Fat, . ‘ A 3°57 2°46 Protein,. . ¥ x 3°50 1:96 Sugar, . z . : 4°98 272 Ash, . ‘ é F O74 0°40 \ ! Percentage of Ice Formed, 16 per cent. Specific gravity, . . 10345 1-009) Per cent. Per cent. Water, . . 85 62 96:23 Fat, : 4:73 12% Protein,. . * 290 0-91 Sugar, . 7 . ; 4°95 1-42 Ash, . * . : 0°80 0:21 It is seen that no appreciable difference between the ratio of the sugar to the protein and the ash is found in the two series of analyses, showing that no separation of any constituent except water takes places during freezing, It is seen that the greater the percentage of the ice separated, the more dilute is the melted ice; this is best seen by calculating the solids not fat (Table LVIL). FROZEN MILK. 205 TABLE LVII.—Composition or Frozen MILK. Percentage of ice, F 1-2 2:0 2 25 0°10 Solids not fat, 5 : 6°17 561 5°08 2°64 Equal to percentage of water (approx.), : 30 38 43 70 As all these samples were taken from churns in which milk was brought up to London, the percentage of ice may be taken as roughly indicating the temperature below freezing point to which the milk was exposed, the time of exposure to the low temperature having been approximately the same in all cases. It appears that the lower the temperature to which milk is exposed the more dilute will be the ice after melting. Composition of Melted Frozen Milk.—The difference in composition between frozen and unfrozen milk may have some importance, should samples be taken under the “Sale of Food and Drugs Act,” in very cold weather; should an excessive proportion of ice be present in the portion sold to the inspector the sample may, though originally genuine, have the composition of watered milk. Vieth has recorded an interesting experiment on the freezing of milk :—Two gallons of milk were exposed to a temperature of — 10° C. (14° F.) for three hours; longer time than this did not render any more milk solid. Ice was formed on the bottom and sides of the vessel employed to contain the milk and a funnel- shaped cavity in the centre was filled with liquid. The ice was found to consist of two layers, one of cream, and the other of skim milk; these were separated as completely as possible and the liquid portion also poured off. The results of analysis were :— Ice. Liquid Portion. Cream. Skim Milk. — j i i Proportion, i é 8°8 percent. | 64°7 per cent.) 26°5 per cent. Specifie gravity, 5 1-0100 10275 | 10525 . Per cent. Per cent | Per cent. Water, . ‘ ‘ ‘ 4-44 92-10 : SOSH Fat, . - ‘ ‘ 19°23 0°68 517 Protein, . ‘ = # 2-64 : 2-80 5°38 Milk-sugar, . . rae 3°33 | 3-95 rat Ash, . O-a2 | 0-60 I Ts 100-16 wo), 100k 206 NORMAL MILK: ITS ADULTERATIONS, ETC. Another experiment gave almost identical figures. It is probable from these experiments that milk exposed to a temperature of — 10° C. will always yield a liquid portion having the composition given above. The figures also show that milk cannot be frozen in blocks, from which pieces can be cut off and melted for use, without modifying the composition to a serious extent. The author has had the opportunity of examining three samples of milk which had been frozen for transport and remelted (Table LIX.). The samples were taken under such conditions as would repre- sent the retailing of the milk. TABLE LIX.—Composition oF Frozen Mix. 1. Il. Wi. Specific gravity, . é 1°0385 1:0270 1:0325 Per cent. Per cent. Per cent. Total solids, . s : 13°60 1013 11°68 Fat, . ‘ é e E 3°29 2°70 2°86 Ash, , 3 - ‘ 0:84 0°62 0-74 Solids not fat, . ‘ : 10°31 7:43 8°82 > No. I. has the composition of concentrated milk, No. II. of a watered milk, and No. III. of a slightly skimmed milk. Attempts have been made to introduce frozen, or partially frozen milk, into the English market from Holland and other foreign countries. The above figures show what may be some- times the composition of milk as retailed, unless extreme care be taken in melting the imported product. 207 CHAPTER IV. THE CHEMICAL CONTROL OF THE DAIRY. ContTents.—Duties of the Dairy Chemist—The Testing of Milk—Deter- mination of Specific Gravity—Estimation of Total Solids—of Fat and Butter — The Control of Milk during Delivery —The Solution of Analytical Problems—Cause of Low and High Specific Gravity—of Sweet Taste—of ‘‘ Poor’ Milk—of unusual Taste and Smell—of Milk being Curdled—of Milk being Thick—Nature of Sediment—Skim Milk—Cream. Duties of the Dairy Chemist.—The duties of the dairy chemist consist in the following :— (1) To see that the milk at or from the farms is of good quality, containing a full percentage of cream, is not tampered with by the employés, and is in good condition. (2) 1f milk is sold by retail, to see that the milk sent out is of good quality, and, by analysing samples taken without notice from the employé in charge of the milk, to ascertain that it is delivered in the same condition as it left the dairy. (3) To see that cream separators, churns, etc., are worked in the most efficient manner, by examining the various products, and to obtain such figures representing their composition as will allow of accounts being kept of the manufacturing processes. (4) To ensure that all products derived from milk are of good quality. (5) To investigate specially products deemed unsatisfactory, and to elucidate the cause for dissatisfaction. (6) To make chemical examinations of water supplies, disin- fectants, etc., so as to ensure that sanitation is carried out by reliable means. (7) To advise on chemical questions that may arise—e.g., the suitability of metals for the construction of dairy apparatus, the examination of waters or boiler compositions for steam produc- tion, the analysis of feeding stuffs and fertilisers, etc. A description of the duties of a dairy chemist must necessarily be somewhat hypothetical, as the conditions in different dairies differ exceedingly from each other. In large dairies the chemist is an official wholly responsible for his own department, and under the control of no one except the proprietor. It is not 208 THE CHEMICAL CONTROL OF THE DAIRY. advisable that he should have any direct control of the business, his functions being those of a scientific adviser; a good dairy chemist should have had a practical experience in dairying, so that he may be able to apply his scientific knowledge to the various points that may arise from time to time. In smaller dairies, the manager or other person may undertake the functions of chemist, and these must be arranged so as to interfere as little as possible with his other duties; this may introduce variations in the plan of work described, by curtailing it, but the general procedure will remain the same. The main duties of the dairy chemist are to see that the milk received from the farms and supplied to the public is pure and contains its due proportion of cream; that the cream and butter are of good quality and of uniform composition ; that the skimmed or separated milk is as poor as possible in fat; and that the water used is free from pollution; as also to elucidate the com- plaints of the customers by examining the product complained of. Samples and Sampling.—The main difficulty in keeping a uniform quality of milk is due to the rising of cream whenever milk is allowed to be at rest. The attention of the chemist should be devoted to studying the conditions under which the milk is distributed in the dairy to which he is attached, and to discover how to prevent this separation of cream during distri- bution. For the proper performance of his duties he must be provided with samples of milk at all possible stages, from the entrance of the milk into the dairy till the final return of the small quantities of milk left after distribution; these samples should, if possible, be examined at once and before the milk has passed to the next stage of delivery. This is only practicable in large dairies where the chemist has no other functions. It is advisable that the persons employed in sampling the milk should be under the control of the chemist as far as this duty is con- cerned, as upon the proper sampling of the milk the whole value of his work depends. In certain cases where more value than usual is attached to the examination, the chemist should person- ally supervise, or even perform, the sampling. The samples may be divided into two kinds, bulk-samples and samples taken during delivery. In the former case, the object to be attained is to take a sample in which the various constituents shall bear the same relative proportion in the sample as in the bulk. In the latter, the bulk from which the sample is taken will be of known composition, and the object of taking the sample is to test the person from whom it is taken; no attempt must then be made to take an average bulk sample, but the person giving the sample should furnish it in the same manner as he SAMPLING. 209 would furnish milk for sale. The taking of the latter class of samples presents no difficulty ; the only precaution to be observed is that the bottle into which the sample is poured is clean and dry, and that it has a well-fitting cork. The proper sampling of a large bulk of milk is by no means easy; the bulk to be sampled will be, in most cases, a churn, and the milk in these should be mixed with a stirrer consisting of an iron rod carrying a perforated tin plate; the stirring is performed by working the stirrer up and down. The “ milk thief,” a trough with a small opening in it, is also employed. The milk to be sampled is made to pass along the trough, and a little trickles out of the hole into a convenient receptacle beneath. This method gives fairly representative samples and requires no labour. Small quantities of milk may be mixed by pouring to and fro from one vessel to another. The samples should then be taken by means of a dipper or, better, by a sampling tube. This consists of a long tube open at both ends, the lower being flat; a flat plate is attached to a rod which runs down the middle of the tube, so that by raising the rod the plate can be pressed against the bottom of the tube enabling it to contain liquid. To take the sample the tube is lowered slowly into the churn, the plate being kept away from the bottom to allow the milk to rise; when the milk has com- pletely filled the tube the rod should be raised, and the tube withdrawn to prevent the exit of the milk; the sample can then be transferred to a convenient receptacle by placing it under the tube and depressing the rod. Another method of sampling bulks of milk, which is scarcely less exact than the preceding, is to tip the contents of the churn into a strainer with sides, the slope of which causes the milk to be thrown from side to side at an angle of 45°. The milk finds an exit through the wire gauze at the sides of a circular well, which should dip into a small tank of such size that the milk rises to the top of the wire gauze; a hood at the back prevents spilling and facilitates mixing. The sample should be taken from the tank with a dipper or sampling tube. This method of sampling has the advantage of removing any particles of straw, dust of food, etc., that may be found in the milk. If the tank be provided with a tap the milk can then be run off. A convenient method of taking a composite sample of all the churns received from one farm is by the use of a large tin pot provided with a spout, which extends from top to bottom, and which communicates with the pot throughout its whole length by a series of holes ,4; inch diameter, about } inch apart. The samples from each churn are emptied As pot, 210 THE CHEMICAL CONTROL OF THE DAIRY. and the composite sample is taken by pouring out from the spout. cnet Samples.—lIt is sometimes convenient to test the milk from a particular source once a week, or at other inter- vals; in this case the specific gravities should be noted daily, and a measured portion, such as 11 ¢.c. or 1 0z., placed each day in a bottle containing a little solid potassium bichromate; the fat estimation is made on the mixed sample. Sample Cans.—The most convenient receptacles for the samples from bulk are round cans about 2 inches in diameter and 43 inches deep, or wide-mouthed glass bottles which can be closed by a disc or stopper. In large dairies, the milk is received from different farms, and it is convenient to stamp the name of the farm legibly on its own sample can; sample cans should be provided and marked for all the samples it is desired to take regularly, and the use of unmarked cans, cans marked with paper labels, and cans marked with another designation should be avoided, if possible. The lids of these cans should fit well, and they should not be filled more than three-quarters full, to obviate as far as possible the risk of spilling in transit. The samples, after being taken, should be placed in a box or tray made to contain twenty-four cans, or any other convenient number, in which they can be transported to the laboratory. The trays should have a strong handle in the middle, and it is desirable that they be also fur- nished with a lid which can be locked or sealed, to prevent any tampering with the samples in transit. The duty of conveying the samples should be entrusted to one man, who should be made responsible for any spilling of the contents. A tray holdin twenty-four cans is not too heavy to be carried steadily, an there is no reason why any of the milk should be spilt. If the sampling is performed at a distance from the laboratory, the use of bottles is more reliable; a case to contain these should be provided. It is, of course, necessary for the chemist to see that the sample cans are in good repair; any which leak, or have ill-fitting lids, should be replaced at once. The cans or bottles before being handed over to the samplers should be quite clean and dry; the cans should be washed with hot water and dried, and when not in use, kept with the lids open. If bottles are used a large stock should be kept, and they should be well washed with warm water and allowed to drain for a couple of days; this will be found to dry them sufficiently. Testing.—The tests applied to milk should be of two kinds, simple tests done in the dairy, and a more extensive examina- tion in the laboratory. The only test sufficiently convenient for use in the dairy is the estimation of the specific gravity. SPECIFIC GRAVITY TEST. 211 This will be sufficient to detect any gross adulteration. The taking of the specific gravity of every churn should be invariably performed, as this indication alone will be sufficient to detect gross adulteration, and it will also give a rough indication of the quality of the milk. For this purpose it is most convenient to employ a thermo-lactometer, or lactometer and thermometer combined in one instrument; the specific gravity should be corrected to 60° F. by means of Table LXXXI. It is not generally necessary that the chemist should personally take these specific gravities. This may be left to a foreman or other intelligent person who has been trained to this work under the supervision of the chemist. The instructions given to the foreman should be, to pass all milk of a specific gravity lying between certain limits, unless special instructions to the contrary in certain cases are given; these limits may be from 1:034 to 1°031, 1:0305, or 1:030, according to circumstances; but in special cases higher or lower limits may be used. Should the specific gravity of any churn fall outside these limits, the foreman should be instructed to take samples with special care, and send them at once to the laboratory to be further tested; the milk in this case should be put on one side and not used until the report of the chemist has been received. As it is possible that a dispute, perhaps in a law court, may arise with respect to these special samples, the fore- man should be instructed to seal both the sample, and the churn from which it was taken, so as to prevent any possibility of the milk being tampered with. This preliminary testing has been found to give satisfactory results in the author’s experience. In all cases where adulteration of milk before arrival at the dairy has been definitely proved, the specific gravity test revealed that the milk was not of normal quality. As an example of a case in which it was necessary to depart from the usual instruc- tions given to the foreman, the author has found, in the case of the milk received from one particular farm, that the milk had a specific gravity as low as 1:029. As the genuineness of this milk was proved beyond a doubt, the lower limit for the milk derived from this farm was fixed for a certain period at this figure. It will not be necessary to teach the foreman to read the lactometer closer than half a degree, as this is an approxi- mation quite sufficient in practice. Undoubtedly, the most perfect control over the milk would consist in the analysis of the milk in every churn before it is used, and the rejection of those churns in which the milk does not come up to the standard of purity adopted. This is, how- ever, hardly practicable in a large dairy, as the milk must be dealt with and sent out as soon as it arrives, and the time for analysis is short. It has been found that the time required for 212 THE CHEMICAL CONTROL OF THE DAIRY. handling a churn of milk—z.e., straining and transferring to the vessel in which it is sent away from the dairy—is about 35 seconds, and the quickest analysis, other than the taking of the specific gravity, occupies at least two minutes ; so that to test each churn in this way would mean delaying the handling of the milk to an extent which is incompatible with the proper working of the dairy. The testing of the milk in the laboratory that has passed the specific gravity test must, therefore, be done after the milk has been disposed of. It has been found that it is not necessary in this case to test the milk in every churn, as the results are for guidance as to the quality of milk that may be expected from different sources, and one sample per day from each farm is sufficient for this; the morning and evening meal should be sampled alternatively. If adulteration is detected, or if the milk is of abnormal quality, the whole of the churns from that particular farm should be tested. It is also desirable to test the whole of the churns from each farm at intervals, say once a month, in order to see that the difference between them is not excessive. No strict rule can be laid down for the taking of samples; the chemist must use his discretion, based on experi- ence, as to what samples he will have taken. Analysis of the Samples.—The cans should be brought at once to the laboratory and the lid of the tray opened; the samples are then to be arranged in alphabetical or numerical order, or in any way that may be most convenient ; a methodical system in this respect will be found to minimise any chance of error in dealing with large numbers of samples. The procedure must vary in different dairies; if the samples are very few, the samples taken at different times of the day may be left till a sufficient number have accumulated and all examined at once. In this case, it is necessary to preserve them in a cool place, especially in summer; but where the time can be found it is preferable to make two or three series of analyses a day. An examination of the lids of the cans should be made to see if any of the milk has been splashed upon them, and if it is not possible to obtain a new sample the portion adhering to the lid should be washed down into the can with some of the sample. The analysis should comprise the following data :—Specific gravity, fat; and total solids, and (by difference) solids not fat. The specific gravity should be estimated by means of a lactometer. The fat may be estimated by the Leffmann-Beam or similar methods, or may be calculated from the total solids and specific gravity. The total solids may be estimated by evaporation, or may be calculated from the fat and specific gravity, The choice of how the analysis is to be conducted will depend upon the time available. The most reliable mode of work is to estimate both LACTOMETERS. 213 fat and total solids, but it requires a considerable amount of ‘time; if this cannot be done, it is most satisfactory to estimate the fat and to calculate the total solids, as the fat is the most valuable constituent of the milk, and also because the accuracy of this estimation by the Lefimann-Beam methods is rather greater than the accuracy of the total solid determination. In some dairies payment is made according to the amount of fat in the milk; in this case, the fat estimation should certainly be made. The Testing of Milk. In this chapter methods requiring less attention in detail than those previously described, and suitable for the use of persons who have not had a thorough analytical training, are described. The results obtained by these methods have not the rigid accuracy which can be obtained by the best gravimetric methods, but determinations approximating sufficiently nearly to the truth can be made, to enable them to be used in practical work. Determination of Specific Gravity. Lactometers.—This is invariably done in milk-testing by lactometers (see p. 214); the lactometers used in dairy work are of two kinds, the thermo-lactometer and the ordinary lactometer. The thermo-lactometer (Fig. 17) consists of a stem on which is marked a double scale, one part reading the specific gravity, and the other the temperature on the enclosed thermometer; a cylindrical body ; and two bulbs, the upper one being the bulb of the thermometer, and the lower one (containing mercury or shot) serving for the adjustment. By its means the tem- perature and specific gravity can be read off from the same instrument. The ordinary lactometer consists of a stem carrying a scale on which the specific gravity is read; a cylindrical, or globular, body ; and a bulb containing mercury or shot. Soxhlet’s lactometer (Fig. 18) contains a scale from 25° (1-025) to 35° (1:035) divided up into suitable divisions (3 or ,'y). Victh’s lactometer (Fig. 19) has a globular body; it requires a smaller bulk and depth of milk than Soxhlet’s, and is suitable for taking the specific gravity in a half-pint can. The scale reads from 25° to 35°. Quevenne’s lactometer has a scale from 15° to 40°, and marked to show proportions of water added to milk and skim milk respectively. This auxiliary scale is useless. Another form of lactometer, the name of whose inventor is 214 THE CHEMICAL CONTROL OF THE DAIRY. deservedly lost in oblivion, has a scale from 0 to 100, 0 being equal to a specific gravity of 1-000 (water), and 100 being equal Fig. 17.—Thermo-lactometer. Fig. 18.—Soxhlet’s Lactometer. LACTOMETERS. 215 to a specific gravity of 1029. It is of no practical use in milk testing. Still another form is marked M at 1°029, and W at 1:00, the intermediate space being divided into quarters; this form is a mere toy. An instrument has lately been put on the market, which con- sists of a glass tube in which is enclosed a bulb of specific gravity 1:029, which floats in milk above this specific gravity, but sinks ane Stays Fig. 19.—Vieth’s Lactometer. when the specific gravity is reduced below this figure by watering, by warming, or by excess of cream. It provides a harmless form of amusement, but is of no practical use. The best lactometers for use in milk testing are the thermo- lactometer, Soxhlet’s, and Vieth’s. The thermo-lactometer cannot be made very small nor very delicate on account of the enclosed thermometer, and requires a comparatively large bulk of milk; it is thus more suitable 216 THE CHEMICAL CONTROL OF THE DAIRY. for testing in the dairy than in the laboratory, where samples are often limited. It has, however, the advantage of not re- quiring a separate thermometer and a separate operation to determine the temperature. Vieth’s lactometer (Fig. 19) may be used in a can and, if the samples are received in cans, as is often the case in a dairy labora- tory, no transference of the sample is necessary. Soxhlet’s lactometer has a wider scale, and may be conveni- ently used when greater accuracy is required. Galaine’s self-correcting lactometer has a metal ball com- pletely filled with chloroform attached to the bottom, the object being to obviate the necessity of correction of the specific gravity for temperature; the expansion of the chloroform was supposed to compensate the expansion of the milk. Though excellent in theory, it has proved disappointing in practice. Beam’s lactometer is devised to obviate the difficulty of determining the exact point where the surface of the milk cuts the stem. It consists of a specially graduated lactometer and a float, and the reading is made by observing the point on the stem which corresponds with the uppermost portion of the glass tube of the float. In use, it is essential that the stem remain dry. Beam’s directions for use are :—The stem of the lactometer being dry the float is passed over it and allowed to rest on the bulb. The lactometer is then lifted by the point of the stem, and gradually let into the milk. If there is any doubt as to the instrument having found its proper level, the base of the jar may be held firmly to the table by one hand and the jar gently tapped with the other. When removing the lactometer the float should be taken out first, in order to keep the tube dry and-ready for another test. The following directions are due to Vieth :— Use of Lactometer.—In order to determine the specific gravity, the milk is poured into a vessel at least 4 inch greater in diameter than the widest part of the lactometer, and deep enough to allow the instrument to float. A cylindrical glass jar (Fig. 20), with foot, is the most suitable vessel for the pur- pose if Soxhlet’s lactometer or the thermo-lactometer be used ; Vieth’s lactometer may be used in a can or tin cup. The lacto- meter is gradually lowered into the milk to the 25th degree, care being taken that the instrument is entirely wetted by the milk and that no air adheres to it. When released, the lacto- meter will move up and down, and after a little while become stationary. That degree of the scale which coincides with the surface of the milk is then noted. It will be observed that, where the milk touches the vessel and the stem of the lactometer, LACTOMETERS. 217 the surface is not level, but, in consequence of the adhesion of the milk to the glass, forms a curve (Fig. 21). There is no difficulty, however, in ascertaining the extension of the curve sufficiently near, and this has to be allowed for in reading off the specific gravity. When using instruments of ordinary size, the curve will be found to extend to about one-half degree. Lactometers indicate the exact ST specific gravity at a temperature of | 60° F. It is, therefore, necessary, as i i soon as the position of the lactometer has been noted, to remove the instru- ment from the milk, immerse a thermometer, and ascertain the tem- perature. If the temperature is found to be 60° F., the observed specific gravity is correct, but should the temperature of the milk be higher or lower than 60° F., the specific gravity must be corrected Fig. 20.—Glass Jar. Vig. 21.—Lactometer in Milk. by the aid of the Table in the Appendix, which is used as follows : —Find the temperature of the milk in the uppermost horizontal line, and the observed specific gravity in the first or last vertical column; in the same line with the latter, and under the tem- perature, is given the corrected specific gravity. For example— Supposing the temperature to be 51° and the specific gravity 218 THE CHEMICAL CONTROL OF THE DAIRY. 34°, the specific gravity corrected to 60° F. is 32°9° = 1:0329 ; or if the temperature is 66° and the specific gravity 29°, the corrected specific gravity is 29°8° = 1°0298. Never take the specific gravity of a milk without also noting the temperature and correcting to 60° Fahrenheit. Instead of reading from the bottom of the curve and making a mental allowance, the lactometers may be read from the top of the curve and a definite figure (ascertained by a few carefully- conducted experiments) added on. As soon as the specific gravity and temperature have been taken, the corrected specific gravity from the table should be entered in the book provided for the purpose of recording the results. It is not necessary to enter the specific gravity in full, but only the three significant figures; thus a specific gravity of 1:0325 may be entered simply as 325 or 32°5. Though the determination of specific gravity has been de- scribed first, it is found when total solids are to be estimated that it is convenient in practice to proceed as soon as work is commenced with their estimation, as this is an operation which proceeds alone. Only in those cases where the sample is so small that the lactometer will not conveniently float, if the quantity necessary for total solid estimation has been removed, is it usually convenient to take the specific gravity first. Estimation of Total Solids. A number of dishes or capsules, each marked with a separate number and previously weighed, and a pipette marked to dis- charge 5 grammes of milk of a specific gravity 1:032 at a tem- perature of 60° F., are necessary. The dishes should be, if possible, of platinum, and at least 14 inches internal diameter, flat bottomed, and with a rim about 4 of an inch wide; this rim should be considerably wider at one side so as to form a lip on which the number should be legibly stamped. These dishes weigh about 12 grammes and cost £3 to £4 each. They may, however, be replaced by porcelain dishes of about 23 inches diameter, glazed all over; these may be marked by scratching the number on the side with a new file, painting this over with a solution of platinum chloride, wiping off the excess, and igniting the capsule; the number will be marked in platinum. The dishes must be previously weighed on a balance accurate to 1 milligramme, and the weights recorded on a table which should be kept in the balance case. It has been found in practice that, if the dishes be carefully cleaned, monthly weighings of the dishes are sufficient, the average loss in this period for dishes used daily having been found to be about 1 to 2 milligrammes. ESTIMATION OF TOTAL SOLIDS. 219 The dishes should be arranged in a shallow tray—a photo- graphic dish is suitable—according to their numbers from left to right, six or seven in a row, beginning at the bottom—ve.. the side nearest the operator. This arrangement is chosen so that any milk accidentally dropped from the pipette will not fall into a dish which has been previously filled, but into an empty dish which can be easily wiped. The tray containing the dishes should be on the left of the tray in which the samples are placed. The samples should be arranged in order in rows, beginning at the left-hand bottom corner and going upwards— z.e., away from the operator—and should, if in cans, have their lids turned back over the next sample can. The taking of samples for the estimation of total solids is much facilitated by having an assistant to stir the milk. The measurement of the quantities of milk for analysis is done as follows :—The assistant stirs No. 1 can, and when the cream has been mixed the chemist plunges the pipette into the milk and sucks it up till it enters the mouth; it is advisable to throw away this first quantity. The milk is again sucked up, the finger placed over the end of the pipette, and the milk allowed to run down to the mark. care being taken that air bubbles are not included in the portion measured. The pipette is held over dish No. 1 and the finger removed; the milk runs into the dish, and the drop adhering to the end is removed by touching it against the side of the dish; the last drops must not be removed by blowing. Mean- while the assistant has closed can No. | and stirred can No. 2, from which 5 grammes are measured in a similar manner, without, however, washing out the pipette; this is transferred to dish No. 2, and the whole of the samples are taken similarly. The next step is to enter the designation of the samples and the number of the dish into which eich has been placed in a book provided for that purpose; the tray containing the dishes is then conveyed to the water-bath. The water-bath should be of copper, about 6 inches deep, and provided with a lid containing a suitable number of holes in which the dishes can rest: the number of these will vary with the number of samples to be daily examined; it is convenient to have a projecting collar about a quarter of an inch deep round each hole, as this facili- tates the putting on and removal of the dishes, and each should be provided with a lid. If steam is laid on, the bath should be heated by means of a coil laid in the bottom, through which the steam circulates; the exit of this coil should be connected with a condenser, and the condensed steam serves to supply the laboratory with distilled water. If steam be not laid on. the bath must be supported on an iron support at such height as to allow of a burner being placed underneath; in either case an 220 THE CHEMICAL CONTROL OF THE DAIRY. arrangement for keeping the water level constant in the bath is necessary. After the dishes have been for about half an hour on the bath, provided it has been boiling briskly, it will be noticed that a distended skin has formed on the surface of the milk; this must be broken with a needle mounted in a handle, care being exer- cised that no portion of the skin is brought away on the needle. The object of this is to prevent the milk drying in flakes, which may be blown away by draughts, and the estimation lost. Should the dishes be forgotten, or should any other reason prevent the stirring being done at the proper moment, a few drops of water may be added to the milk residue, which will have the effect of making the flakes settle down and adhere to the dish. When the dishes have been on the water-bath for three hours, they should be taken off, placed on a tray having two or three thicknesses of blotting-paper on the bottom to remove adhering drops of water, and transferred to a water-oven or air-bath. The important point akout the water-oven is that it has an even draught passing through it; the form of air-bath devised by Dr. Adams of Maidstone is suitable, though the cover is a little troublesome to remove. The dishes are placed upon wire shelves ane above the other, and it is convenient to have ten or twenty dishes on each shelf. If a good draught be maintained in the water-oven or air-bath, it is not necessary or advisable to keep this at a higher temperature than 90° to 95° C. After three hours drying in the air-bath, the dishes should be weighed. Weighing.—Ten basins (or any number that can be con- veniently placed in the balance case at one time) should be removed from the bath, placed on a tray and conveyed to a desiccator, and there allowed to cool for a few minutes. Plati- num basins cool very much faster than porcelain, and much time is saved by their use; when cool, they should be weighed to the nearest milligramme, the weight entered in the book opposite to the number of the dish; the weight of the empty dish (from the table of weights) should be subtracted, and the weight of the milk residue will be the difference between the two weights; this also should be entered in the book. As 5 grammes of milk were taken, the residue, multiplied by 20, will give the percentage of total solids in the milk. If the samples arrive in the laboratory in sample bottles and not in cans, a somewhat different mode of procedure must be adopted. A number of cylindrical tins without lids (of such a size as to hold the contents of a sample bottle) and a lactometer are necessary. The bottles and dishes are arranged in their proper order and entered in the book, as before. As many bottles as there are tins are shaken, to mix the cream, and emptied ESTIMATION OF FAT. 231 into the tins; 5 grammes are taken from each and placed in the dishes, but before the milk is poured back into the bottle or otherwise emptied from the tin, the temperature and specific gravity should be taken; the remaining samples are then simi- larly treated in their proper order. The drying and weighing are performed as before. Rapid Methods.—A pipette is used which delivers 2°5 grammes of milk, and the milk is run into flat-bottomed porcelain basins about 3 inches in diameter. The numbers are marked on the basins with copper paint, which paint, on ignition, forms an indelible blue mark. Before the basins are filled, Stokes recommends that two or three drops of a 10 per cent. solution of acetic acid in alcohol be sprinkled over each. The alcohol spreads itself over the surface of the milk, and the acid precipitates the casein. Revis adds 1 c.c. of acetone. Under these circumstances, drying proceeds very rapidly. The basins are placed on the water-bath till apparently dry, a matter of a few minutes only, and are further dried for about an hour in the water-oven or air-bath. They are then weighed as before. The difference between the weight of the basin with the residue and the weight of the basin alone, multiplied by 40, gives the percentage of total solids. In the author’s experience Stokes’ method has a tendency to give results slightly above the truth, but according to Yarrow the difference does not exceed 0-08 per cent.; it has, however, the advantages of rapidity and of requiring very little attention. Estimation of Fat. For the estimation of fat in a rapid manner, with an accuracy sufficient for milk control, a centrifugal method must be used. The Leffmann-Beam, and the acido-butyrometric methods, will be described in detail. The Leffmann-Beam Method, and Modifications.—Leff- mann and Beam, realising that the time of whirling necessary in Babcock’s method, which consisted in treating the milk with an equal volume of strong sulphuric acid, and separating the fat by centrifuging, was a serious objection, experimented with a view to shortening this. They finally decided on the use of amyl alcohol as a means of assisting the fat to rise, and were thereby enabled to reduce the time of whirling.* The method is usually employed in conjunction with the Beimling machine. * It was stated in the first edition that the same idea was independently worked out at the Vermont Experiment Station ; but it appears that this was not correct, ard was based on a misunderstanding. 222 THE CHEMICAL CONTROL OF THE DAIRY. The method has been subjected to a close investigation by the author, and is of considerable accuracy. The Beimling Machine.—This consists of a cast-iron frame- work carrying a vertical spindle ; on this is a small bevelled cog- wheel, which engages a larger bevelled cog-wheel on a horizontal spindle turned by means of a handle. In the larger machines a second spindle and set of cogs is introduced (Fig. 22). On the top of the vertical spindle two, three, or six arms extending radially are fixed. To the ends of each of these are pivoted one or usually two cups, in which the bottles are placed. When the handle is turned, the cogs cause the spimdle and the arms carrying the cups to rotate. For one turn of the handle, the vertical spindle turns eleven times. Centrifugal force causes the cups to assume a horizontal position when rotating, and they return to the vertical when the machine is at rest. The bearings are all plain, which causes a considerable amount of friction ; the centre of gravity of the rotating system is placed very high, which causes vibration, due to imperfect balancing, to be marked. The air resistance at high speeds is somewhat great. These are serious faults, but are capable of improvement. The two-bottle Beimling machine is the only machine on the market, to the author’s knowledge, in which the bottles assume a hori- zontal and radial position when rotating ; in the larger sizes the LEFFMANN-BEAM METHOD. 223 bottles are nearly, but not quite, radial. This position is advan- tageous, as it allows of the most rapid separation of the fat from the acid liquid. Apparatus.—The test bottles consist of flat-bottomed flasks with a sloping upper portion terminating in a graduated neck. The bottles (English make) hold 29 c.c.; the necks are made of glass tube 5°96 mm. in internal diameter, and are so graduated that 80 divisions = 1:475 c.c. These dimensions are according to a specification laid down by the author, and differ slightly from those prescribed by Leffmann and Beam. The pipettes used are— 15 c.c. for milk, 9 c.c. for sulphuric acid, 3 c.c. for amyl alcohol mixture, 4°5 c.c. for cream, and 10°5 c.c. for water. Automatic measuring apparatus and burettes may be also used for measuring the acid and amy] alcohol. The author has devised a burette specially for the measure- ment of sulphuric acid and other corrosive liquids. It has been found, in practice, that ordinary burettes are liable to be filled to overflowing, and that considerable inconvenience is caused by spilling strong sulphuric acid. An ordinary burette with a three-way tap is used, and to the tube, for filling from the bottom, a wider tube, 4 inch in diameter and 3 inches long, is fused. An india-rubber cork is inserted in this, and through it is passed a long glass tube bent as a syphon, which serves to convey the acid from a stock bottle above. In the top of the burette an india-rubber cork is fixed, through which passes a tube going almost to the top of an air chamber of class; to the bottom of the air chamber a glass tube of small bore passes upwards so far as just to enter into the stock bottle. The illustration (Fig. 23) will make the construction clear. The conditions necessary for satisfactory working are :— 1. The capacity of air chamber and tube leading to stock bottle must not be more than + of the capacity of the burette. 2. The bottom of the stock bottle must be well above the top of the tube leading into the air chamber. The tube leading into the air chamber must be adjusted to the mark on the burette equal to its capacity. The burette is used as follows :—The tap is turned so that the liquid enters and fills the burette. As it reaches the upper portion, it passes up the tube and overflows into the air chamber, from which it is forced up the tube leading to the stock bottle. When the liquid reaches a height corresponding to the level of the liquid in the stock bottle, the liquid ceases to run, and the 224 Fig 23 —Automatic Burette. burette is automatically filled to the zero point. When the tap is turned the liquid runs out, air bubbling in from the stock bottle, and measured quantities may be taken. After the liquid has been run out as far as desired, the tap is turned, and the liquid enters the burette. The liquid in the air chamber is forced back into the stock bottle, and the burette automatically fills itself. The burette can be made of 9 ¢.c. capacity, but it is much quicker to employ a graduated burette of much larger capacity than any form of automatic measur- ing apparatus. The advantages claimed for the burette are— (1) Automatic filling to zero point. (2) One turn of the tap only required to fill and to measure. (3) Impossibility of spilling corrosive liquids. (4) Saving of time, as the filling is done while other operations are conducted, Chemicals. — Commer- cial sulphuric acid con- taining 96 per cent. H,S80,, which has a specific gravity of 1°842 at 15°5° C. (60° F.). Owing to the fact that strong sulphuric acid has a@ somewhat anomalous specific gravity, it is not advisable to test the specific gravity directly. The fol- lowing test will give good LEFFMANN-BEAM METHOD. 225 results :—Measure accurately 200 c.c. of acid into a large flask, and to it add cautiously 15 c.c. of water, cooling the flask by immersion in cold water. Take the specific gravity of this diluted acid, either with an accurate hydrometer or by other means. If the temperature be not exactly 15°5° (60° F.), add on 0-001 for each degree Centigrade above 15°5°, or 0:00056 for each re Fahrenheit above 60° F. (or subtract for temperatures elow). ; The following table will give the strength of acid :— Specific Gravity of Diluted Acid. Per cent. H280.. 1°8380, F 2 : ‘ : ‘ . 98 (94-20) 1°8349, . ‘ * ‘ A " . 97 (93 22) 1°8311, z ‘ ; 3 i % 96 (92°24) 18268, 7 ‘ 2 ‘ ‘ » 95 (91°26) 1 8217, ‘i i ‘ F . ‘ 94 (90 28) The figures in parentheses give the percentage of sulphuric acid in the diluted acid, the other figures referring to the per- centage of acid before dilution. Another method of determining the strength of acid is to weigh about 1 gramme of acid in a basin and, after diluting with water, to add an excess of strong ammonia. The solution is evaporated on the water-bath and, when nearly dry, a little more strong ammonia is added; it is then dried to constant weight at 100° C. (212° F.) and weighed. The weight divided by 1°347 will give the weight of sulphuric acid in the sample ; this, divided by the weight taken and multiplied by 100, will vive the percentage. Purified amy! alcohol, free from petroleum, specific gravity 0°815 to 0°818 at 15°5° C. (60° F.), which completely dissolves to a clear liquid when mixed with an equal bulk of hydrochloric acid; this mixture must not become darker than sherry in three days. Commercial hydrochloric acid. The amy] alcohol is mixed with an equal bulk of hydrochloric acid for use; it is best not to keep this mixture longer than a few days. The Process—Testing of Milk, Skim Milk, Buttermilk, and Whey.—Measure 15 c.c. each of the well-mixed samples into test bottles, holding the point of the pipette against the side of the neck, so that the liquid may run down, allowing room for the air to escape. Add 3 c.c. of the mixture of amyl alcohol and hydrochloric acid. Pour in, with care, 9 c.c. of sulphuric acid, so that it washes down any particles of milk on the neck of the bottle. Mix the contents of the bottle with a rotatory motion; a little practice is required to do this without the liquid boiling over, owing to the heat evolved on mixing 15 226 THE CHEMICAL CONTROL OF THE DAIRY. sulphuric acid with water, but when the way is once learned there is no difficulty in doing this. Fill up the bottles to the zero mark with a mixture of one part of sulphuric acid to two volumes of water, and place the bottles in the machine; rotate by turning the handle at 100 revolutions per minute for about one minute, when the fat will separate in a clear layer. Read the fatty layer as follows :—Note the position of the lower surface of the fat (it 1s convenient to wait till it has fallen to one of the main graduation lines), then immediately note the position of the lowest point of the curve on the upper surface ; the difference between the two will give the per- centage of fat; repeat this once or twice; the results should be identical (Fig. 24). Each small division is ~, per cent. fat; if, then, the fatty layer occupies thirty-six of these, the percentage is 3°6. Half or a quarter of a division may easily be read with practice. Should the fatty layer have sunk below the lowest graduation, a little more diluted acid may be added, and the bottle whirled for a few seconds. In very cold weather the fat may solidify in the neck; in such case it should be warmed slightly before reading; it is not otherwise necessary to warm the bottles before reading. Skim milk and buttermilk should be whirled as - soon as possible after mixing ; in very hot weather, — or if the bottles stand very long after the acid has = been added, the fat may be of a dark colour. It is advisable to compare the results given by = this method with those given by the Gottlieb or other good gravimetric process whenever a new stock of sulphuric acid or amyl alcohol is used, and, if necessary, to work out a definite correction to be added to or subtracted from the results. } With acid and alcohol corresponding to the specifi- Fig. 24. cation above, no correction should be necessary. Neck of bottle, The difference between the results by the Lefimann-Beam method and those by gravimetric analysis very rarely exceed Ol per cent. of fat. Testing of Cream.—If the cream contains less than 32 per cent. of fat it can be measured direct by the 4°5 c.c. pipette; if it is thicker than this, it must be diluted with separated milk. Two beakers or tin pots are counterbalanced on a rough balance turning to 0°01 gramme ; in one of them, about 25 grammes of cream are placed, and water is run into the other till the weights are equal. The cream and water are mixed together, and the (DON LEFFMANN-BEAM METHOD. 227 mixture can be measured. If the cream is sour a few drops of ammonia should be placed in the pot before the weights of water and cream are adjusted. The measurement is performed as follows :—Fill the pipette with cream by sucking at the top, and close it with the finger ; hold the pipette vertically, and allow the cream to run down till the upper surface is on a level with the mark; turn the pipette to a horizontal position and wipe the stem ; then return it to the vertical and, holding the point over the neck of a test bottle, allow the cream to run out freely ; after the quick succes- sion of drops has ceased allow three more drops to run. Add 10°5 c.c. of water and proceed as in analysing milk. Calculate the results from Table LX., using column 3 for undiluted cream and column 2 for diluted cream. This table should be checked by gravimetric analysis whenever a new pipette is used. TABLE LX.—For Estimatine Far 1x CREAM. Reading. Diluted. Undiluted. Reading. Diluted. Undiluted. S'5 63°'8 320 67 49'8 Us 8-4 63-0 31°6 66 49-0 24°6 8:3 62-2 31:2 65 49-2 pe Be sie 61°4 30°8 64 47-4 23°8 8:1 60°6 30°4 6:3 46°6 234 8-0 599 30°0 6:2 459 23°1 79 59'1 29°6 61 45°] 22°7 78 58°3 29-2 6-0 44-4 229 7 57°6 289 Bg A3-G be | 76 56°8 Uae 58 42°8 215 rcs 56:0 28"1 57 a | ed Nag 74 55°3 27°7 56 41] °4 20°8 is) 545 27°38 55 40°6 20:4 Ce, 53°7 26°9 oa 39°S 20:0 71 52°9 265 «|| 58 391 19°6 70 52°1 26°1 aw 38°3 19-2 6-9 5l-4 25-8 51 375 1S'S GS 50°6 25'4 5-0 86°7 ses | Testing of Sour Milk.— Weigh in a small beaker about 15 wrammes of the sample which has been previously well mixed by whisking with a brush formed of fine wires; pour as much as possible: into a test bottle and re-w eigh the beaker: the differ- ence will give the weight of the milk taken: add sufficient water to make up to 15°25 yrammes and proceed as in analysing milk. Calculate as follows :—Multiply the reading by 15°25 and divide by the weight taken: the result will be the percentage cof fat in the sour milk. 228 THE CHEMICAL CONTROL OF THE DAIRY. Testing of Clotted Cream, Cheese, and Butter.— Weigh the bottle and transfer to it about 1 to 15 gramme of butter, 2 grammes of clotted cream or 3 grammes of cheese, and weigh again. Butter should be melted in a closed vessel at a tempera- ture of 40° C. (104° F.), and, after shaking, about 13 c.c. sucked up in a tube which will just enter the neck of the bottle; the butter should be blown in as completely as possible. Clotted cream should be well mixed and sucked up in a tube in the same way as butter, and either blown or pushed in with a wire. Cheese should be cut up into small pieces, which can be dropped in. Add sufficient water to make up the weight to 15°25 grammes and proceed as in analysing milk. Cheese requires rather longer shaking than other products, but gives equally good results. If desired, cream may be weighed instead of being measured. The calculation is performed as for sour milk. The above directions differ in some respects from those given by Leffmann and Beam. The author has had, however, some years practical experience of the methods described and is con- vinced of their accuracy. A stand for the bottles is to be recommended ; this may conveniently be made of wire rings into which the bottles fit, with a flat plate for a bottom; the bottles can then be easily carried about. To clean the bottles: empty while hot in a convenient recep- tacle, and wash twice thoroughly with hot water; if necessary, tun a brush down the neck. They are conveniently washed in the stand. Never leave pipettes dirty. Failures and their Probable Causes.—The only failures likely to happen are :— 1. Dark layer of fat. 2. Fluffy layer under the fat. 1. If the acid be too strong, or the temperature too high, or the mixture left too long before whirling, the fat may be dark. The remedy is obvious. 2. A fluffy layer under the fat is often caused by allowing the milk and acid to stand too long unmixed. It may sometimes be due to a bad quality of amyl alcohol. Grit on the bottom of the bottles may cause fracture while in the machine. Fracture may also occur from too sudden a stoppage after the whirling is completed. Modifications of the Leffmann-Beam Method. — The Leffmann-Beam method has been subjected to considerable modification ; thus Paterson and, later, Gerber have used amyl alcohol alone without hydrochloric acid. Gerber’s Acido-butyrometric Method.—This is essentially the Leffmann-Beam method, the chemical principles of which GERBER METHOD. 229 have been adopted. The use of hydrochloric acid as a solvent for the amyl alcohol has been, however, discarded, following Paterson. Gerker employs a test bottle, which he terms an “ acido- butyrometer,”’ which differs from that employed by Leffmann and Beam; it is a modified form of Marchand’s lacto-butyrometer, and, like this, is closed with a cork. A definite strength of sulphuric acid is prescribed (90 to 91 per cent.), and rules for testing the acid and amyl alcohol used are laid down. Gerber has shown considerable ingenuity in adapting the method of Marchand to that of Leffmann and Beam, and the method is reliable. The following comparative statement will show the differences of detail between this and the Leffmann-Beam method :— LEFFMANN-LuAM. GERBER. 1, Test bottles are flasked-shaped. _ Test bottles are butyrometer-shaped 2. 96 per cent. sulphuric acid is 90 to 91 per cent. sulphuric acid is used, used. 3. A mixture of amyl alcohol and = Amy! alcohol alone employed hydrochloric acid employed. 4. Fat read off cold. Fat read off at 60° to 70° C. 5. Bottles are used open. Bottles are stoppered. There is no practical advantage in either method. The original Leffmann-Beam is somewhat more rapid, while the Gerber modi- fication requires rather less skill. Both are equally accurate. I. The Tester with Catgut Action for Four and Eight Samples (Gaertner and Hugershoff’s Patent)—Description.—. A steel spindle, running in two ball bearings, the upper with ten balls and the lower with seven, is supported in a well-stayed frame, which can be fixed to any table by means of a screw clamp. On top of the spindle is a boss, on which two discs with screw threads are fastened, which hold the disc-plate for the reception of four or eight samples. The cover is screwed on to the spindle by means of a loose milled-headed nut and the machine is ready for use. If the machine is destined for frequent use, it will be best to fix it to a strong bench and not to a movable table ; to strengthen it further, two screws may be put in through the holes in the frame and the tester will then not be transportable. The bearings can be adjusted by} means of the brass collar in the upper one which is held in place by two screws: this should be so arranged that the spindle runs easily without play, and when this is found to be the case, the screws should be tightened to hold the collar in place. The bearings should be oiled with good machine oil, care being taken that the oil which runs down the spindle is wiped off. 230 THE CHEMICAL CONTROL OF THE DAIRY. To rotate the machine, put the metal end of the catgut into the hole in the spindle, wind the string around, by turning the disc-plate backwards till the handle is close to the spindle. Pull the handle with full strength, the whole weight of the body being brought to bear, and as the string unwinds the machine is rotated ; when all the string is unwound the end comes out of the hole, and the machine rotates freely. If clean and well oiled it will run for ten minutes. To stop the machine, take hold of the milled-headed nut of cover firmly and it will screw itself off; then press the edge of the under disc-plate gently with the finger till it stops. Do not stop it with a jerk. II. The ‘Excelsior’? Gearing.—This can be fitted to 8- or 24-sample machines. It consists of a hollow cylinder fixed to the frame carrying a hollow double pulley, inside which: the spindle can rotate without touching. Round the lower portion of the pulley is coiled a spring, and in the opposite direc- tion round the upper a strap is wound, which passes through an opening in the cylinder; on the strap is clamped a stop-plate, which serves a double purpose—(1) to prevent the spring from pulling the strap too far, and (2) to lift the pulley, which 1s capable of a slight vertical movement, when the strap is wound home. At the bottom of the pulley is a pawl, which when the stop- plate is pulled out, engages a ratchet wheel on the spindle and which is lifted with the pulley when the stop-plate is home, so that the pulley runs freely. The machine is rotated by pulling the handle on the end of the strap rapidly to and fro fifteen to twenty times, when a high velocity is obtained; the strap and stop-plate are then allowed to go home and the machine runs alone. If the speed slackens, it can be increased by a few further pulls. This gearing is only recommended for 24-sample machines. III. The ‘“ Rapid’? Gearing.—lIn this, a loose pulley sur- rounds the spindle; it runs on a separate bearing and is, when not in use, kept up by a spring. A strap passes round the loose pulley, and when this is pulled (in a slightly downward direction) the pulley is brought downwards; two bevelled teeth engage two similar teeth on the spindle and cause the machine to rotate. When the strap is pulled back (in a slightly upward direction) the spring forces the pulley up and the machine rotates freely. By pulling the strap rapidly backwards and forwards, a high rate of speed can be obtained. The 2-bottle machine differs in construction from the others in not having the disc-plates, which are replaced by two arms, carrying cups; these cups are larger than the cups used in the larger machine and have a cover; the test bottles fit completely into them and are surrounded by warm water. GERBER METHOD. 231 The machine is fitted with the “Rapid” gearing, and has plain bearings; this causes continual driving to be necessary. The machines cannot be left to run alone. None of the methods of driving the Gaertner-Hugershoff machine are satisfactory. The catgut requires a strong pull and is liable to soon wear out, if the metal end comes off; if it is required to rotate a second time, the machine must be stopped. The “ Excelsior”? gearing has a weak point in the spring, which breaks and is difficult to repair; the strap also sometimes breaks, and cannot be replaced without some trouble. The * Rapid” gearing makes an unpleasant noise, and a great deal of the power employed to drive the machine is wasted in friction. It is far better to discard the methods of driving sold with the machine and to employ a yard of blind cord (of the best quality), one end of which is fixed into a wooden handle. This is given one or two complete turns round the spindle ; the handle is held in the right hand and the loose end in the left. The cord is pulled with the right hand, just sufficient tension being kept on the end with the left to make it bite. At the end of the stroke, the left hand is brought up near the machine to loosen the cord round the spindle, otherwise there is danger of the cord winding up. The cord is now pulled back with the left hand keeping it quite Joose—z.e., letting the mght hand go back quite freely. The pulling with the right hand is repeated, and continued till the speed is high enough. It is advisakle to stop up the hole in the spindle, as it causes the cord to wear. Should the cord wear out and break, it can easily be replaced at an infinitesimal cost. This method of driving was worked out in the author’s laboratory by Boseley and Rosier. The Lister Machine.—This has practically the same form as the Gaertner-Hugershoff machine, but does not include the * Excelsior” or * Rapid” gearings, which are covered by patents. The frame is of different construction, and is S-shaped. Round the spindle a small brass pulley is fixed * (in the 24-bottle machine a ratchet is added), and it is driven by a string wound round this by Boseley and Rosier’s method, which, however, was independently applied by Lister. The 2-bottle machine has the arms hinged. and clamped in place by a screw, instead of having them in one piece; it 1s more easily portable. *In practice it is better to take off this pulley, stop up the hole, and drive on the spindle direct. The machines have also been made without the pulley. 232 THE CHEMICAL CONTROL OF THE DAIRY. There are many other machines now on the market, which in general principle are much the same as the original Gaertner- 7. Fig. 25.—Gerber Tester. Hugershoff centrifuges. Some of these are driven by a handle (Fig. 25), which, by means of a worm gearing, imparts a rapid Fig. 26.—Gerber Tester, electrically driven. motion to the spindle, and this method of driving finds favour with those who do not mind the extra expense, GERBER METHOD. 233 Steam turbines, water turbines, and clectro-motors (Fig. 26) are also largely used as the motive power, especially with large machines. Apparatus, etc.—1l. The acido-butyrometer is a glass vessel closed by an_ india-rubber cork, and with a graduated neck divided into ninety divisions; one division = 0°] per cent. fat. Every tenth division is longer than the others, and the intermediate fifth divisions are _ also slightly lengthened to facili- tate reading, The neck may be either round, as in Gerber’s original butyrometers, square section for extra strength, and flat for ease in reading (Figs. 27 and 28). A special acido-butyro- meter is made for skim Ee milk; the upper portion of E the neck is narrowed, and the divisions are much wider. 2. The acido-butyrometer for cheese, etc., is open at both ends, and the lower cork carries a small glass cup. 3. The author’s butyro- meter stand consists of a metal plate pierced with 4, Bec 3, or 24 holes, and an india- & ‘ubber plate with 4, 8, or 24 = sorresponding holes so cut [Ee chat the butyrometers are slid easily in and out and yet ire retained when inserted. 4. 11 cc. pipettes for milk vith, or without, automatic neasurement. 4a. 3° vc. pipettes for ream, 5. 1 c¢.c. pipette for amyl alcoho). 6. A water pipette, 10 c.c. in 5 cc. 6a. A water pipette for cream, delivering 8°2 c.c. ca Figs. 27 and 28.—Gerber Bottles. 234 THE CHEMICAL CONTROL OF THE DAIRY. 7. 10 c.c. bulb pipette for acid. The bulbs prevent the acid from being drawn into the mouth. 8. Automatic measuring apparatus, or burettes, as an alter- native means of measurement. Chemicals.—Commercial sulphuric acid, specific gravity of 1°820 to 1°25 at 15° C. (59° F.) (contains 90 to 91 per cent. H,80,). The specific gravity may be taken with a hydrometer. Fig. 29.—Amyl Alcohol Fig. 30.—Acid Measure for Gerber Measure for Gerber Test. Test. Should the temperature not be exactly 15° C. (59° F.) the specific gravity may be corrected by adding on 0-001 for each degree Centigrade (or 0°00056 for each degree Fahrenheit above 59°) above 15°, and by subtracting 0-001 for each degree below 15° ; thus, if the temperature be 20° and the specific gravity 1°818, the corrected specific gravity will be 1:818 +5 x 0-001 = 1:823; GERBER METHOD. 235 and if the temperature be 11° and the specific gravity 1°827, the corrected specific gravity will be 1°827 — 4 x 0-001 = 1°823. Pure amyl alcohol—specific gravity, 0°8165 to 0°818 at 15° (59° F.); boiling point, 124° to 130° C.—should give a clear solution with an equal volume of strong hydrochloric acid. Amyl alcohol sometimes contains petroleum, due to the use of empty petroleum barrels as packages. A blank test with the Gerber method fails to reveal the presence of petroleum if the quantity is below 2 per cent., a quantity which gives an error of about 0:2 per cent. in the fat estimation. It may be detected by running 10 ¢.c. of sulphuric acid, 10 c.c. of water, and 2 c.c. of amyl alcohol into a Gerber butyrometer, mixing and centrifuging; no layer should appear if the amyl alcohol be free from petroleum. If present an approximate estimation of the quantity may be made; the following results were obtained by the author and Goodson :— TABLE LXI. Percentage of ‘ Error witl Error witl Fewolewin, Reading. Whole Milk. shut atestGA Mlk 2. | | 4:8 0-67 + 0-38 + 0:37 | 24 0-25 + 0:27 4 le 12 ; O-ll | + O13 + 0:07 0-6 t trace t + 0:09 + 0-08 O35 doubtful trace -- Q-02 x | none ; none | og os It is advisable to have a bottle of ammonia handy in case acid is spilt on the clothes; should this happen an application of a few drops of ammonia at once will prevent damage. If strong acid is spilt on the skin, wash copiously with cold water without delay and the white swellings formed will soon disappear. Mode of Operation. Milk, Skim Milk, Whey and Buttermilk.—Place a sufficient number of acido-butyrometers in the stand, open end upwards, aud run 10 c.c. of acid into each. Well mix the samples to he tested and measure with the milk pipette, 11 c.c. of each into the bottles; add 1 ¢.c. of amyl alcohol. Measuring liquids by means of pipettes is done as follows :-— Hold the pipette near its upper end between the thumb and the middle finger of the right hand, insert the lower tapering 236 THE CHEMICAL CONTROL OF THE DAIRY. end into the liquid, and fill it by exhausting the air with the mouth, then remove the lips and quickly close the upper end by means of the first finger. The pipette is then removed from the liquid, and by raising the first finger slightly, so much of the contents are allowed to escape, drop by drop, until the lowest point of the curve forming the surface of the liquid coincides with the mark on the upper part of the instrument. The con- tents are then discharged, the pipette being allowed to run out. Insert the corks, slightly damping them at the ends if neces- sary ; place the hand over the corks and shake with an up and down motion until the curd is dissolved; invert the stand to allow the acid in the lower bulb to mix with the rest, and thoroughly mix the contents by inverting three or four times. Take the bottles out of the stand one by one and allow the con- tents to run into the larger portion, push up the cork, if necessary, so that the graduated neck is full, and place the bottles in the cups of the machine, screw on the cover and spin it for two or three minutes. Place a Bunsen burner, with a flame just high enough to touch the bottom of the disc-plate, underneath to prevent cooling, unless the machine is fitted with a, steam turbine, or with one of Gerber’s heaters, which will keep it at the neces- sary temperature. If the fat is not in a clear limpid layer in the neck, or if the upper portion is frothy, the rotation has not been sufficient and must be repeated. After taking out the bottles, Gerber directs that they be placed in the water-bath for about a minute, which must be kept at a temperature of from 60° to 70° C.; they are then ready for reading. The water-bath may, without sacrificing accuracy, be dispensed with if the disc is kept warm. It is an advantage to use a flame, as the corks have a tendency to come out in the bath, thereby spoiling the estimation. Reading the Fatty Layer—Hold the butyrometer up to the light, and by slight pressure on the cork adjust the bottom layer to one of the larger lines on the scale; count up the number of divisions between this and the lowest curved line at the top; each of the larger divisions is equal to 1 per cent. of fat, and the smaller ;4; per cent. of fat; every fifth smaller division is also made somewhat longer to facilitate reading. In the illus- tration (p. 226) the percentage of fat shown is 3°6; observe that the lower layer is coincident with one of the longer lines, and that the lower curved line at the top is thirty-six smaller divisions above that. All pipettes are graduated to run out; therefore the liquids must not be blown out. Separated milks require to be whirled for a somewhat longer GERBER METHOD. 23 time and at the highest attainable speed, and 0:05 per cent. must be added to the reading. Condensed milks, both sweetened and unsweetened, may be tested by weighing about 20 to 25 grammes, making up to 100 c.c., and treating as a milk; a higher speed or longer whirling is, however, necessary to get up all the fat. The percentage of fat found must be multiplied by 100 and divided by the weight taken. C'ream.—Cream containing not more than 32 per cent. of fat can be measured with great accuracy. In the case of thin cream —i.e., one with not more than 32 per cent. of fat—after the acid has been added, add 8:2 c.c. water, measure the cream with a 3 c.c. pipette, filling it up accurately to the mark while in a vertical position, turn the pipette in a nearly horizontal position, and wipe the stem perfectly dry; hold it over the bottle in a vertical position and, removing the finger from the top, let the cream run out freely; after the quick succession of drops has run out, allow three more drops to enter the bottle ; add 1 c.c. of amy] alcohol, and then proceed asin analysing milk. Calculate the results from Table LXII., column 2. Creams containing more than 32 per cent. of fat must be diluted. Take two beakers or tin pots and counterbalance them on a rough balance turning to 0:01 gramme, pour about 25 grammes of cream into one and add separated milk or water to the other till the weights are equal, mix the cream and sepa- rated milk or water, and measure as before. Use column 3 for calculating the results. TABLE LXII.—For Catcunatine Fat 1x CREAM. Degrees. Undiluted. Diluted. Degrees. Undiluted. Diluted. | 1 — ame | 35 33:2 66-2 6-7 25-9 516 S-4 32 8 65-4 66 25°5 50S 8:3 B24 64°6 65 25-1 500 | 82 32-0 63°8 6-4 24:7 492 $1 316 62 9 63 24:3 48-4 8) 31-2 62:1 62 239 47 6 7 30-7 61:3 61 23 5 46-8 e FCB 30°3 60°5 60 23°1 46:1 fe ORG 29-4) 59°77 59 22-7 45°3 | 76 29-5 58 9 58 22:3 44:5 eds 29+] 58°] 57 21-9 43-7 1 pee 28'S 57-3 56 215 42:9 | 73 23:3 a6 4 5°5 211 42:1 72 27-9 55°6 54 207 413 | oa 34:8 533 20-3 40°5 TO | 271 FS ct 19-9 39-7 69 267 | 582 | 51 19-5 38-9 | 68 | 26°3 524 | 50 19-1 38 1 | | | 238 THE CHEMICAL CONTROL OF THE DAIRY. This table should be checked by a gravimetric method, and may require a slight correction added or subtracted, which may vary with each pipette. The cream should be as near 15°5° C. (60° F.) as possible, but the error due to temperature is very small and is less than the errors of reading, etc. The pipette does not deliver the same weight of a cream with 20 per cent. of fat as of one with 30 per cent. of fat; this has been allowed for in the table. Sour Milk.—Well mix the sample by whisking for a few minutes with a brush made of fine wires ; pour about 15 grammes into a small beaker and weigh; transfer from 10 to 11 grammes to the bottle and weigh again to get the weight added; add water to make up 11:22 grammes. Proceed as before. 11-22 Calculate: Fat in sour milk = reading x -, —~——: wt. taken An alternative method is to add to each 100 grammes 5 c.c. of strong ammonia and treat as a milk; increase the result by -one-twentieth. Clotted Cream, Butter, Cheese, ete—Well mix the sample (in the case of butter it is advisable to melt it in a closed vessel at about 40° C. (104° F.) and to shake violently till solid). Place a few grammes in a small basin with a glass rod and weigh. After adding acid, transfer, with the rod, from 1 to 2 grammes (according to percentage of fat, 1 for butter, 1°5 for clotted cream, and 2 for cheese) ; add water to make up to 11°22 grammes and 1 c.c. of amyl alcohol, and proceed as before. Calculate as for sour milk. To Clean the Bottles—After reading, place the bottles in the stand, cork upwards; take out the corks and wash them several times with hot water. Do not use soda. Empty the bottles into a suitable vessel and fill them with hot water; empty this out completely and repeat twice ; if not quite clean run a brush down them and wash again. Invert the stand and let the bottles ‘drain. Dry the corks after use. Never leave pipettes dirty. Keep the stopper in the sulphuric acid bottle when not in use. Gerber recommends a butyrometer with two openings for solid products; the lower cork carries a little glass cup of 1 c.c. capacity, and the product to be tested is weighed into this. The author has not found this advantageous. Cream and Clotted Cream.—Well mix from 50 to 100 grammes -of the sample to be tested, fill the cup with this, dry the outside and weigh. Place the cork carrying the cup in the butyrometer, add 6 c.c. of clear hot water through the upper opening, then 1 c.c. of amyl alcohol and 6°5 c.c. of acid, and shake well; add GERBER METHOD. 239 6 c.c. more hot water, shake again and whirl in the machine. Read after one minute’s standing in the water-bath. Butter —Melt about 10 to 20 grammes in a small closed bottle at 40° C. (104° F.) and shake violently till solid; fill the cup, and weigh. Add 12 c.c. of cold water, and 1 ¢.c. of amyl alcohol and 6°5 c.c. of acid. Shake well and proceed as before. Cheese.—Mix 10 to 20 grammes in a mortar till of even con- sistency. Fill the cup and weigh; transfer the bulk of the cheese from the cup to the butyrometer, by inserting the cork and shaking gently ; add 6 c.c. of hot water and 6°5 c.c. of acid and shake till the cheese is dissolved. Now add 7 c.c. of hot water and 5 drops of amyl alcohol (from the pipette), shake well and whirl in the machine. Stop the machine after about two to three minutes, take out the butyrometer, add a further 1 c.c. of amyl alcohol, and place for a minute in the water-bath at 60° to 70° (say 150° to 160° F.); whirl again and read after a minute’s standing in the water-bath. For Skim Cheeses whirl three times and add 8 ¢.c. of hot water instead of 7 c.c. Calculation of Results —The percentage of fat in the sample is found by dividing the number of degrees read off on the stem of the butyrometer by the weight taken, thus 25) Butter wt. 0°76 gramme. Reading 62° Fat = ie = §1°6 per cent. : ° 490g Cream wt. 0°90 “is 5 49P 5 = 090 = 544 vo Oo? , 4 90° = Tt = 39-35 Cheese wt. 0°68 = ai 22" = 6-68 32°35, Water Estimation in Butter, Margarine, cte.—A special form of butyrometer is used for this; it consists of an elongated bulb 5 c.c. in capacity, connected by a graduated tube with a vessel in which a cork carrying a cup of 3 ¢.c. capacity is inserted. The only reagent necessary is diluted sulphuric acid, made by diluting commercial sulphuric acid (sp. gr. 1820 to 1°825) with an equal bulk of water; before use this should be cooled to the ordinary temperature, and decanted from any deposit of lead sulphate. Five c.c. of diluted sulphuric acid are measured into the buty- rometer, which is placed open in the machine, and whirled for about two minutes, in order to bring all the liquid into the bulb ; the level of the acid (at as near 60° F. (15°5° C.) as possible) is read off on the graduated scale. About 2} to 3 grammes of butter are weighed into the cup, and after the cork has been inserted, the butyrometer is stood in the water-bath at 60° to 70° C. (say 150° to 160° F.) to melt the butter; when this has 240 THE CHEMICAL CONTROL OF THE DAIRY. been accomplished, the whole is well shaken till the contents form a uniform emulsion; after standing for a minute in the water-bath, the butyrometer is placed in the machine, and whirled three times, warming in the water-bath for about two minutes between each; after the third whirling, it is cooled to as near 60° F. as possible, and the level of the aqueous liquid where it joins the fatty layer is read off. The difference between this reading and the level of the acid will give the percentage of water if exactly 3 grammes of butter have been taken; should any other weight have been taken it is necessary to multiply the result by 3 and divide by the weight taken; thus, in an experiment 2°780 grammes of butter were taken, the level of the acid was 2°5° and the level of the aqueous liquid 14°5°; the percentage of water indicated is, therefore, Se a = ae = 12-95 per cent. water. For the convenience of weighing out the cream, butter, etc., in the cups, a balance of the steel-yard type can be obtained with the machine ; it consists of a beam, with suitable supports, one end of which is longer than the other; from the shorter end, which also carries a pointer, a small wire cradle to support the cup is hung; the longer end is divided into 10 equal parts, each being indicated by a notch numbered 1 to 10; at the end of this is a fine screw carrying a counterpoise, which can be moved backwards or forwards by screwing round. The weighing is accomplished by placing the cup in the cradle, and screwing the counterpoise backward or forwards, as required, till the pointer is at zero in the middle of the scale; the cup is now removed and filled with the product to be tested, and the riders are put on the various notches in the beam in succession till equilibrium is restored. The largest rider indicates grammes, the medium tenths of a gramme, and the smallest hundredths ” of a gramme. Thus if the largest rider is in notch 2, the medium 7, and the smallest 8, the weight is 2°780. If it be found that to restore equilibrium it is necessary to place the smallest rider intermediate between two notches, say between 2 and 3, the reading is taken as 0°025. If it be found that two riders must be placed on the same notch to restore equilibrium, the smaller should be hung from the upturned end of the larger. The use of this balance, though convenient when many samples are being tested, is not necessary, as the weighings may be made, but slightly less expeditiously, with an ordinary balance. Stokes’ Modification.—Stokes employs a modification of the GERBER METHOD. 24] acido-butyrometer ; it is open at both ends, one being provided with an indiarubber washer kept in place by a screw cap, while the other can be closed with a cork. It is placed screw cap downwards: up to the zero mark of the graduations, the tube holds 1°5 c.c., and the neck is graduated to read percentages of fat; the upper portion consists of two bulbs ; from the zero mark of the graduations up to a mark between the two bulbs the bottle holds 13°5 ¢.c., while from this mark to a mark above the second bulb the capacity is 15 c.c. It may be used without a centrifugal machine as follows :— 15 c.c. of amyl alcohol are poured in to the zero mark, or, better, measured by means of a pipette provided with a rubber teat of about 1 ¢.c. capacity; sulphuric acid is carefully poured in to the mark between the bulbs, and then the milk to be tested is poured in to the upper mark. An indiarubber cork is put into the upper opening, and the contents of the butyrometer well mixed by shaking and inversion. The tube is now stood, cork downwards, in hot water, the screw cap loosened, and left for an hour; the fat will have collected in a layer in the graduated neck, and can be read off in the same manner as previously described. This forms an extremely cheap method of estimating fat in milk, with an accuracy quite sufficient for most purposes, and can be recommended where only one or two samples per day are to be tested. The apparatus can be used also .or the more exact estimation of fat by measuring the milk, acid, and amyl alcohol by means of pipettes, or automatic measuring apparatus, and whirling in a centrifugal machine. The Lister-Stokes machine is made to take these bottles; it differs chiefly from the Lister-Gerber in the form of the disc. Instead of having a lid, the disc is made double and open in the centre, the butyrometers being slid into cardboard tubes in pockets, which are symmetrically arranged, radiating from the centre. This form of machine has the advantage of having the pockets comparatively large, and can be used for other purposes. The whole of the disc can be conveniently filled with hot water should it be desirable to prevent cooling during centrifugal separation. Alkaline Butyrometric Methods.—Gerber has devised a method whereby the use of sulphuric acid is avoided, and this has found favour among those persons who have not had the ad- vantage of a laboratory training. The composition of the alkaline salt solution has not been made public; the method is employed with the same apparatus as the acido-butyrometric method. 16 242 THE CHEMICAL CONTROL OF THE DAIRY. Eleven c.c. of the alkaline salt solution, 10 c.c. of milk, and 0°6 c.c. of isobutyl alcohol are placed in a butyrometer, which is closed with a stopper, and the contents mixed, and immersed in water at 45° for three minutes, and after shaking the tube is centri- fuged, and the fat read off after again placing in water at 45°. These results are the same as those given by the acido-butyro- metric method, but the accuracy is somewhat less. The amount of isobuty] alcohol added must not be varied. Sichler’s sinacid method is very similar; 10 c.c. of salt solution, containing 15 per cent. of trisodium phosphate and 1 per cent. of trisodium citrate, 10 c.c. of milk, and 1 c.c. of isobutyl! alcohol are placed in a butyrometer, and well mixed. The mixture is heated to 75° to 90°, again well mixed, and centrifuged for one minute. The tube is placed in water at 70°, and the fatty layer read off. The isobutyl alcohol is usually coloured, and the colour passes into the fatty layer, facilitating reading. The Control of Milk during Delivery to Customers. A very important part of the work of the dairy chemist is the control of the men employed in delivering milk. It is evident that a man on a milk round, being under no supervision for a greater part of the time, has ample opportunities, should he be so disposed, to adulterate or ‘“‘ lengthen” the milk of which he has temporary charge. He may also, with the best intentions possible, unwittingly deteriorate the quality of the milk by allowing the cream to rise on the milk, and serving some cus- tomers with the richer portion, thereby leave a poorer quality for others. For the purpose of this control it is necessary to take three series of samples. (1) Samples representative of the mixed bulk of milk that is placed in charge of the man. (2) Samples taken in the streets in the course of delivery. (3) Samples of the small quantities of milk returned. The first and third samples should be taken by a foreman or other responsible person, preferably in the presence of the man; the foreman should be responsible for their conveyance to the laboratory. The second series should be taken by an intelligent and respons- ible person, who should receive instructions te take samples at irregular intervals, and to avoid any semblance of rotation, in order that the man shall not be able to form an idea when he may expect a visit. He may be, with advantage, mounted on a bicycle if the area of delivery is large. The first and third series may be conveniently taken in sample cans, while the second series may be taken in five-ounce bottles, CONTROL DURING DELIVERY. 243 which have been found to hold sufficient milk for analysis, while not being too large to be easily carried. A case holding a dozen bottles should be provided for this purpose. The testing of these samples may be performed largely with a lactometer ; in fact, it is in this work that the usefulness of the lactometer is most appreciated. The specific gravity of the samples of series (2) and (3) should be carefully compared with those of series (1), which will form a standard by which the others may be judged. In all cases the specific gravities must be corrected to 60° F. Three cases may occur. 1. The specific gravity of a sample of series (2) or (3) is equal to the specific gravity of the corresponding samples of series (1). In by far the greater number of cases this indicates that the composition of the samples is identical. It is possible, however, that the milk may have been skimmed, which would raise the specific yravity, and then slightly watered, which would bring the specific gravity back to the original dearee, It is, however, excessively unlikely that a milk carrier could perform this feat with such accuracy as would be required, and an experienced observer would have his suspicions aroused by the thin appear- ance of the milk. It is also patent that a man adulterating milk for the sake of profit, or with malice, would not confine himself to one isolated occasion, but would do so h: abitually ; and only a skilled scientist could habitually remove cream from milk, and reduce its specific gravity to the original degree by watering. For all practical purposes it may be taken that when the specific vravities auree the milk has not been tampered with. 2. The specific gravity of the sample of series (2) or (3) 1s higher than the specitic gravity of the corresponding sample of series (1). This indicates that it contains less cream than the original. 3. The specific gravity of the sample of series (2) or (3) 1s lower than the specific gravity of the corresponding sample of series (1). This may be due to two causes—either the milk * contains more cream than the original, or it has been watered. In some instances both causes may be responsible for the lowness of the specific gravity. If the second or third cases have occurred, a further examina- tion of the milk should be proceeded with. Either the fat or total solids should be estimated, and the solids not fat calculated ; the corresponding sample of series (1) should be simultaneously examined. It is advisable that the samples— vr a selected number of them—should be examined if it has been found that the specific gravities agree, as it affords a means of checking the accuracy of ‘the specitic gravity determinations, 244 THE CHEMICAL CONTROL OF THE DAIRY. and of detecting the somewhat hypothetical case of scientific skimming and watering. A very important rule, which is of great use in the control work of the dairy chemist, may be enunciated as follows :— The specific gravity of a milk in lactometer degrees added to the percentage of fat will remain constant, whether the cream has been diminished or increased. The sum of the two will be lowered by the addition of water. For instance, the original milk had a specific gravity of 1:0325 or 32°5°, and contained 4 per cent. of fat. The sum is, therefore, 36°5. If a sample of (say) series (2) were found to have a specific gravity of 1:0315 or 31°5°, and contained 5:0 per cent. of fat, the sum would be still 36°5. If the sample had a specific gravity of 10335 or 33°5°, it will be found that the fat amounted to only 3°0 per cent., and the sum would be 36°5. If the sample, however, contained only 3°8 per cent. of fat, and had a specific gravity of 31:5°, the sum would be only 35°3 ; and it could then be concluded that the milk had been watered, and that it contained only x 100 = 97 per cent. of the original milk, or, in other words, 3 per cent. of water had been added. It has been found that this rule holds with remarkable accuracy for any percentage of fat between 0 and 10, and it is not very far out with even higher percentages of fat. It must not be expected that the sum of the lactometer degrees and fat will always add up to the same identical figure, as there is a liability to error in both determinations ; with care, however, the difference due to this cause should not. exceed 0°5. The value of the samples of series (3) lies in the fact that rising of cream is most easily detected by their percentages of fat being considerably different from that in series (1), as the total effect due to this cause is usually marked. The Solution of Analytical Problems.—A dairy chemist is frequently called upon to solve the most diverse problems with regard to milk and its products. In the following paragraphs a few such problems are given, together with the analytical data from which the solution was deduced. They cover a fairly wide range, and may be taken as fairly representative of the questions a dairy chemist is called upon to elucidate. All are actual examples. Prosiem I.—To determine to what the low specific gravity of the milk is due. THE SOLUTION OF ANALYTICAL PROBLEMS. 245 Example a—The analytical figures were :— Specific gravity, . 3 ‘ z - 10234 Total oer : : 5 ‘ ‘ . 9°82 per cent. Fat, . : x ‘ a2) - Ash, ‘ is ‘i . P - 051 y Solids not fat, 6-61 33 From the extreme lowness of all the figures it was concluded that 26 per cent. of added water was present. Example b.—The analytical figures were :— Specific gravity, . Z ‘ : : - 1-0300 Total solids, F < . 3 . 11-46 per cent. Fat, . ‘ ‘ a 4 : ; » 833 4s Ash, 2 . : . : 0-68, Solids not, fat, ‘ ‘3 ‘ 8-13 53 In this case it was concluded from the low solids not fat, and the correspondingly low ash, that a small amount (5 per cent.) of added water was present. Example c.—Two samples of milk taken from two churns arriving at a station from a farm. The analytical figures were :— No. 1, Mie Specific gravity, . - 10234 1-0298 Total solids, . 9-19 per cent. 11-6 per cent. Fat, . . 2:07. ss 3°30 ,, ‘Ash, 055 ., O69 ,, Nolids not fat, : ~ WR 4. N31 es In this case analyses of milk from the same farm had been made for some time previous, and the solids not fat had not been found to fall below 8°6 per cent. It was concluded that No. 1 contained 24 per cent. and No. 2 3 per cent. of added water. The conclusion about No. 2 would not have been justified had there not been evidence of the normal composition of this milk. Erample d.—The analytical figures were :— Specific gravity, . : : ‘ 1-0291 Total solids, . 2 12-78 per cent. Fat. . : , 436 ,, Ash, . : ‘ . j ‘ 0-73 33 Solids not fat, ‘ ‘ ‘ F 8-42 - Genuine authenticated samples from the same source had been found to contain as little as 8°28 per cent. of solids not fat. It was, therefore, concluded that this sample was genuine, but abnormally poor in solids not fat. 246 THE CHEMICAL CONTROL OF THE DAIRY. Example e.—The analytical figures were :— Specific gravity, . : é . 1/0292 Total solids, : . 11-57 per cent. Fat, . ; ¥ « val 9 Milk-sugar, . F ‘ . 341 s5 Casein, ) : Albumin, | te BEB as Ash, . 3 F : . OS8l ,, Solids not fat, i , F . 8-06 we It was concluded from the abnormally low proportion of milk- sugar, and high amount of casein and ash, that this sample was. genuine, though of abnormal character. Example f—In this case the composition of the original milk was known. The analytical figures were :— Sample Submitted. Original Milk. Specific gravity, . . 10311 10325 Total solids, . 12-03 per cent. 12-46 per cent. Fat, . ‘ : « 845 5, 355, Solids not fat, . . 8-58 55 891, The sample contained 3 per cent. of added water. Example g.—The analytical figures were :— Specific gravity, . : ‘ ‘ « 10287 Total solids, . , . p . 16°75 per cent. Fat, . i , . 8-10 5 Solids not fat, : : é P @- 8:65 os, The low specific gravity was due to an excess of cream; this is shown by the high percentage of fat, and the comparatively high amount of solids not fat. Example h.—The analytical figures were :— Specific gravity, . J F . 10245 Total solids, d : : . 16-11 per cent. Fat, . ‘ . i : : . 821 ,, Ash, . : : , ; é . 065 ,, Solids not fat, . ‘ i ‘ ‘ . 790 ,, This sample contained a large excess of fat, but had also received an addition of 8 per cent. of water, shown by the low solids not fat and small amount of ash. Prostem II.—To determine cause of high specific gravity of milk. Example a.—The analytical figures were :— Specific gravity, . - 10346 Total solids, ; - 10-95 per cent. Fat, . . 180 ,, Solids not fat, é » O15 2” The low fat shows that this milk has been deprived of a portiom (40 per cent.) of its cream. THE SOLUTION OF ANALYTICAL PROBLEMS. 247 Exam ple b.—The analytical figures were :-— Specific gravity, . . , . 10363 Total ae ‘ ; ‘ . 13-86 per cent. Fat, . , ‘ 5 3-62, Milk. -sugar, . ; ‘ 5 r . 458 3 Protein, . : : » 462 * Ash, . % ; . O82 ,, Solids not fat, F ‘ ‘ 7 : . 10-24 From the abnormal ratio of protein to milk-sugar, it was concluded that this milk was genuine and of abnormal compo- sition. Example c.—The analytical figures were :— Specific gravity, . . 2 2 é . 10614 Total solids, . 20-84 per cent. Fat, . é ‘ ; 473, Milk-sugar, . ; a S86 4, Protein, ; i r i F . 6:02 de of which Albumin, ‘ ¥ , : . trace. Ash, . j : : ‘ a 123) 45 The practical absence of albumin showed that the milk had been boiled; the high figures shown by milk-sugar, protein, and ash indicated that the milk had been concentrated, and that this was the cause of the high specific gravity. Prose III.—To determine cause of sweet taste of milk. Erample a.—The analytical figures were :— Specifie gravity, : . 10352 Total solids, ; . 11-53 per cent. Fat, . i : « 296 es Ash, . ‘ : 0-80 se Solids not fat, : : 4 . 997 ” The normal ratio of ash to solids not fat and their excessive amount point to the milk having been concentrated. This milk had also been deprived of a portion of its cream. Example b.—The analytical figures were :— Total solids, : ‘ ‘ ‘ . 16-23 per cent. Fat, . ‘ » 205 or Milk- sugar (polarised), . i z . 15°83 % a3 (g paasimetric), « S:l2 58 Ash, . F ‘ = 10559: Solids not fat, é - » 14-18 3 The extreme difference between the polarimetric and gravi- metric figures for milk-sugar points to the presence of added sugar, probably cane sugar in aqueous solution. This sample may possibly have been a diluted condensed milk. 248 THE CHEMICAL CONTROL OF THE DAIRY. Example c.—The analytical figures were :— Specific gravity, . 2 ‘ - ‘ 1-0293 Total solids, 3 é 2 . 10-21 per cent. Fat, . é : : : Z 243, Milk- -sugar, . : 4 ‘ i ; : 512 Ca, Protein, : ‘ e . 2-25 - Ash, . ; . O41 ,, Solids not fat, ‘ : ‘ : E . 7:78 The low ash and protein point to the presence of 35 per cent. of added water; there has also been an addition of milk-sugar, probably to mask the addition of water. Prostem IV.—To determine reason for milk being called “ee os poor. It is evident that either watering or abstraction of cream would cause the milk to appear poor; it is unnecessary to give further examples of this kind. Example a.—The analytical figures were :— Specific gravity, . 3 . 10326 Total solids, 13-45 per cent. Fat, . . 430 ,, Albumin, 0:10 ~—,, Ash, . 0-75, Solids not fat, é 915, Cream in six hours, 5 13 >”? This milk was normal in composition and contained a good percentage of cream. The low albumin and small amount of cream thrown up in six hours showed that it had been boiled. It was probably the slow rate of rising of cream, due to the milk having been raised to a high temperature, that caused a suspicion of ‘‘ poorness.”’ Example b.—The analytical figures were :— Specific gravity, . 10325 Total solids, 12-70 per cent. Fat, . . &78 ,, Solids not fat, 8-92 % Colour, ‘ . quite white. The fat was also seen to be neatly colourless. The milk was of good quality, but of a very white colour, probably due to the cows having been fed on artificial food. The “ poorness’’ was here evidently judged by the colour. The widespread belief that absence of colour denotes poorness has led to the artificial colouring of milk. Example ¢.—The analytical figures were -— Specific gravity, . : . 10317 Total solids, 3 14:11 per cent. Bat, x é - 5:04 a Ash, F : 0-75 ” Solids not fat, é : f : - 9:07 THE SOLUTION OF ANALYTICAL: PROBLEMS. 249 This milk was unusually rich ; it is probable that it contained an excess of cream. It was the other portion of the milk (which naturally was deficient in cream) that was poor. Prostem V.—To determine reason of unusual taste and smell. Example a.—The smell was faint and like stale fish, and the taste soapy and unpleasant. The following were the analytical figures :— Specific gravity, . F 3 : ‘ . 10364 Total solids, : 5 . 3 : . 11-56 per cent. Fat, . f ‘ ‘ ‘ : » B89 - Ash, : 105 ,, Solids not fat, 9-17 ” The milk was alkaline and the ash titrated with phenol- phthalein ; had an alkalinity equal to 0°33 per cent. of Na,CO.,. It was concluded that an addition of 0°3 per cent. of sodium carbonate had been added. Exanple b.—The milk smelt of vinegar and curdled on warming. The analytical figures were :— Specific gravity, . ‘ 1:0329 Total solids, ‘ i 12-45 per cent. Fat, . ' ‘ . 3:50 9s Ash, . é ‘ r ‘ é . O74 Pn Solids not fat, i ‘ x , i » 895 5 Acidity, . : ; : : . 50° The milk was curdled by phosphoric acid ; 60 c.c. of the whey were distilled :— The first 10 c.c. took 1:3 ce alkali », second “a a » FS x 2? third * 19 > 39 It was evident that the milk contained an acid somewhat less volatile than water; this corresponds with acetic acid, and the whey distilled as a solution emomtesnite O-1l per cent. of acetic acid, which is equivalent to 2 per cent. of vinegar. Example c.—The milk had a faint burnt taste. It contained 0°42 per cent. soluble albumin. On centrifuging, a deposit was obtained which appeared to consist of proteid matter; it was much browned. It was there- fore concluded that the milk had been placed in a vessel, in which burnt milk had previously been kept. 250 THE CHEMICAL CONTROL OF THE DAIRY. Example d—The milk tasted burnt. The following analytical figures demonstrated that the milk had been boiled :— Fat, . : . 8°72 per cent. Cream i in six hours, ‘ 1:3 35 Soluble albumin, . : Z a; ‘ . trace. It was concluded that the milk had been burnt in boiling. Example e-—The smell and taste were unpleasant, but could not be identified. The following analytical figures were obtained :— Specific gravity, 1-0292 Total solids, 13-22 per cent. Fat, . 2 : : ‘ ‘ Z « 482 4; Milk-sugar, . é : és . 434 ~~ ,, Protein, ¥ % 4 ° . 3°36 “ Ash, . 0-70—y, Solids not fat, 840, The sediment obtained by centrifuging contained much mucus and cells from the udder. It was concluded that the milk was the product of a cow in ul health. It is evident that if dirty water has been added to milk, an evil smell and taste may occur; no further example need be given of this. Turnips and other substances eaten by the cow or, what is more likely, handled by the milker, may communicate a taste to the milk. The action of certain organisms may have a similar effect. The author is unacquainted with chemical methods of identifying these causes. Prositem VI.—To determine reasons for milk being sour or curdled. Example a.—The acidity was 17°5°, and the cream in clots. The analytical figures were :— Specific gravity, . : - 10333 Total siti : , . ‘ . 12-73 per cent. Fat, . . ‘ : > 8 O6 9 Ash, 2 : F ‘ , . O76 ,, Solids not fat, ‘ ‘i i « IT 33 Soluble albumin, . é . none, Taste, ‘ 3 3 ‘ boiled. The milk had been boiled and the cream allowed to rise and clot, giving the milk a curdled appearance. THE SOLUTION OF ANALYTICAL PROBLEMS. 251 Example b.—The milk was curdled, and the whey was analysed. Acidity, . * : » 43-1° Total solids, , ; . 625 per cent. Fat, . ‘ : F « 103° 4; Ash, . ; . O45 4, Solids not fat, ts ; 2 » 520 2 From the low percentage of solids not fat and ash of the whey, it was concluded that about 15 per cent. of water had been added, and there was some probability that this water con- tained an acid. It may also have been watered milk which has gone sour. Example c.—The milk was curdled and the whey analysed. The analytical figures were :— Acidity, : i 352° Total solids, : : . 7-46 per cent. Fat, . ; ‘ : . O88 ,, Ash, ‘: . ‘ ‘ . OO ,, Solids not fat, : : é 658 ,, It was concluded from the fatibel percentage of solids not fat and ash of the whey, that nothing had been added and that the milk had become sour by natural causes. Example d—The milk was curdled and the whey analysed. It was slightly bitter and gave a pink biuret reaction. The analytical figures were :— Acidity, : . . 20°87 Total soli, : ‘ i . 11-13 per cent. Fat, . : : : » 3:03 Ash, . ‘ ‘ ; » OD ,, Solids not fat, ; ; . 810 i The alkalinity of the ash to Pionvipi@hetetn was equal to 0-025 per cent. Na,CO,. It was concluded that the milk had been peptonised, and was insufticiently alkaline. Exrample e-—The milk was curdled and the whey analysed. The following were the analytical figures :— Acidity, 262 Total solids, . . 9-42 per cent. Fat, . AEB an Milk-sugar, . 7 “DS ay Ash, . F » 60 # Solids not fat, . 815, The milk was not bitter, but gave the biuret reaction. It was concluded from the low acidity and the high milk- sugar that lactic fermentation was not the cause of curdling ; from the biuret reaction being obtained, it was concluded that an enzyme was the cause. 252 THE CHEMICAL CONTROL OF THE DAIRY. Milk is often alleged to be sour because when used for making milk puddings and custards with eggs, a clear whey runs out. The curdling of the milk is due to the coagulation of the large amount of albumin of the egg on baking. The following is an analysis of a whey from rice pudding :— Total solids, ‘ . . 17-67 per cent. Fat, . : ‘ i . 0-82, Ash, . ‘ ; : : . O85 ,, Solids not fat, . 4 ‘ : 4 - 16:85 ,, It was very sweet and contained much cane sugar. Fig. 31.—Microscope. Proptem V1I1—To determine the reason for milk being thick. Example a.—The analytical figures were :-— Specific gravity, . . ‘ ‘i . 10262 Total solids, ‘ : 3 3 . 17-92 per cent. Fat, . ; s : . 9-36, Ash, . ; : : ‘ &. SOFT 3s Solids not fat, . é : . 856 2” SKIM MILK. 253 This sample contained an excess of cream, which made it appear thick. Example b.—The sample gave a blue colour on adding iodine solution. It was thickened with starch (or flour). Example c.—The milk was thick and, on dipping a glass rod into it and lifting it out, a stringy mass adhered to it. On putting the rod (which had been sterilised) into a bottle containing sterilised milk, the latter acquired the same property in twenty- four hours. The milk was “ ropy.” Prosiem VIII.—To determine the nature of sediment. In cases of this description, the milk should be placed in tubes and centrifuged; as much milk as possible must be decanted, distilled water added, and the tubes again centrifuged; this procedure should be repeated till the water is clear. The sedi- ment is examined microscopically (Fig. 31). Vegetable cells, if clear and sharply defined (Fig. 32), are usually due to the bark of hay and the dust of cake given to the cattle during feeding time. If indistinct and stained yellowish or brownish, these usually indicate cow-dung (Fig. 33). Small hairs, cotton and woollen fibres usually show the pre- sence of household dust. Crystalline particles usually indicate road dust. In this case a little of the deposit is placed on a slide and warmed with dilute hydrochloric acid, which is evaporated nearly off; a drop of water is added and also a drop of a solution of potassium ferro- cyanide. A blue colour, due to iron, is obtained from road dust. An estimation of the dit may be made by allowing the milk to stand, and measuring the amount in a graduated tube (Fig. 34). Skim Milk.—The term ‘skim milk ”’ is applied to milk from which the bulk of the cream has been abstracted. Two ways of abstracting the cream are practised: (1) by allowing the milk to stand, taking advantage of the force of the earth’s gravity to separate the cream; (2) by employing centrifugal force to attain the same object. Distinction between Skimmed and Separated Milk.— A distinction has been drawn between skim milk obtained by these two methods; that obtained by setting the milk being called ‘skimmed milk,” and that obtained by centrifugal force “separated milk.’’ The distinction is one of degree, not of kind, as, were it possible to keep milk without chemical change for an indefinite period, the same result would ultimately be obtained. by either method. 254 THE CHEMICAL CONTROL OF THE DAIRY. Fig. 32.—Dirt in Milk. Fig. 33.—Dirt in Milk. SKIM MILK. 255 The following are the characteristics of skimmed and separated milks :— SKIMMED MILK Contains the solids not fat of the whole milk, partially changed by the action of micro-organisms. Contains usually more than 0-4 per cent. of fat. Contains a portion of the solid im- purities of the milk. H lsd 4 | —-| | TTT ae Ui, HR TP arms SEPARATED MILK Contains the solids not fat of the whole milk, practically un- changed. Contains usually less than 0-3 per cent. of fat. Is free from the xo id impurities of the milk. Fig. 34.—Dirt Estimation in Milk. The term machine-skimmed milk is adopted in the Sale of Food and Drugs Act, 1899. Rising of Fat Globules.—The globules of fat rise through the milk because they are lighter than the milk serum. If we have globules of fat of radius 7, the force impelling it to rise will be proportional to the weight of an equal bulk of milk 256 THE CHEMICAL CONTROL OF THE DAIRY. serum less the weight of the globule, or f=b dar — deg, where & is a constant varying with the units adopted for 7, ds and d;. z is the ratio of the circumference of a circ‘e to its diameter, r is the radius of the globule, and g is the acceleration due to gravitation. ds and dy; are the specific gravities of the serum and fat. The globule does not, however, rise freely ; at the velocity at which the globules move the resistance is very nearly proportional to the square of the velocity. We may then write the equation :— Total force at any moment impelling the globule to rise is— _ k.tart. (ds — dg — cv? by equating k 4x. (ds — d,)g. to b?, leaving only the variables, we may write this— “ = Bb? 73 — ev, Integrating this, we get-— C= br. (e@! — 1) el + el) ” where a = 2br’. For large values of ¢ the expression Pt will approach very nearly to 1, and the equation becomes very nearly equal to v = ae or, expanding this by substituting the value of b, we get— € Vk. tx (de — dj) gq. ; : a c is the coefficient of viscosity of theserum. It is evident that equilibrium will be after a short time established when the resisting force is equal to the impelling force, and if the latter be constant the motion will be uniform. The time taken by a globule to pass through a given layer of milk is, therefore, inversely proportional to the square root of the cube of the radius. If the globule is acted on by centrifugal force, the expression ps cal be must be substituted for g. 3,600 V = velocity in revolutions per minute, b = distance of globule from the centre of revolution. If submitted to centrifugal force, it is evident that the speed of a globule cannot be constant, as the centrifugal force tending to move it varies with the distance of the fat globule from the centre of revolution, and the equation for the motion of globules under these conditions is— d?s 4x Vb ds\ ? gab te 4) Se 8)" Solving this equation and integrating between the limits b and b,, we get— THEORY OF CREAM SEPARATION. 257 _,rav 2(d. — d,) b t=k, 30 “ me by which expresses the time taken for a globule to pass from any point in the separator to any other point, provided the serum is at rest and the globule travels radially. This is not the case in modern separators where the milk runs in con- tinuously, and terms expressing the rate of flow of milk, and the shape of the separator, must be introduced. The resulting equations are so complex that it would serve no useful purpose to deduce a general equation. Whatever the form of equation suited to any particular separator, the time taken by a globule to pass through w given space will always be pro- portional to the square root of the cube of the radius, and as the number of gallons per hour passed through the separator will be inversely propor- tional to the time, it follows that for each size of fat gobule there will be a limit where its velocity against the stream of milk will be equal to the velocity of the stream itself, and all globules smaller than this will pass out with the separated milk. If we assume that the total weight of fat in globules of any size is equal to the total weight of fat in globules of any other size, it follows that the amount of fat in the separated milk is pro- portional to the cube root of the square of the number of gallons per hour The coefficient of viscosity, and also the value of the factor (ds — d,), vary with the temperature, and consequently the viscosity of the fat globules and the amount of fat in the separated milk. The relative proportions of the cream and skim milk will also effect the percentage of fat in the separated milk, as not only is the rate at which milk travels towards the separated milk outlet effected, but any resistance to the exit of cream causes the fat globules to touch each other, and interferes with their free motion. The author has, upon these considerations, worked out « formula to give the percentage of fat in the separated milk— 3s 40 - t) ( : A f=axbd eee 2 where / = percentage of fat in separated milk, K= s » cream, t = temperature in degrees Centigrade, m = number of gallons per hour, v= revolutions per minute. a, b, and c are constants for each separator. b usually varies from 1-035 to 1-05. é eA oe from 1-00 to 1-05. ¢ is appreciable, chiefly with separators in which the adjustment of the thickness of the cream is made at the cream outlet—e.g., in the Alpha separator, in which c has the value 1-U4 to 1-05. The following results were obtained with a separator, for which the following formula was applicable :— on ae F mi ‘x 10471" x 4. (4 f = 8,155 x 1-046 a ; 17 258 THE CHEMICAL CONTROL OF THE DAIRY. TABLE LXIII. F . m. o. Bs f eale. Per cent. Degrees. Gallons. Revolutions. Per cent. | Per cent. 15°5 32 35 5 00 0°05 0-04 42:0 32 350 5600 0-12 0:13 51:0 32 350 5600 0°175 0'194 52°6 32 350 £600 0-210 0°207 56'3 32 350 5600 0-247 0246 65 0 32 350 5600 0°330 0369 60°4 38 350 5600 0:22 / 0-228 62+1 38 350 5600 0°25 0 247 51:0 32 240 5600 0-14 0°14 53:0 27 350 5600 0:30 0°27 42:0 32 325 5200 015 Old 70-0 76 120 5600 0:07 0-07 The constant a depends on the following conditions :— 1. Size of drum and thickness of the layer of milk. 2. The specific gravity of the milk serum and of fat. 3. The units in which the variables are expressed. The first condition is that which can be varied by a difference in type of separator. The constant b chiefly depends on the viscosity (internal friction) of the milk serum ; also, to a slight degree, on the cubical expansion of milk serum and milk fat, and on the friction of the liquid against the drum. The constant ¢ depends on the viscosity of cream and on the friction of the cream against the sides of the outlet. It is naturally advantageous for a, b, and ¢ to be as low as possible. To obtain a low, the drum should be of large capacity and the formation of currents in the milk should be prevented ; the discs placed inside the drum in separators of the Alpha type ensure the latter condition, and, therefore, decrease a. To obtain 6 low, the exits, and especially the cream exit, should be as large as compatible with the proper working of the separator ; and the tubes, through which the skim milk and cream leave the drum, as short and as straight as possible. To obtain c low, cooling of the cream inside the drum should be avoided, and the cream exit large. Separators in which the adjustment of the thickness of cream is performed at the cream exit have a large c. It is more difficult to express by a definite formula the amount of fat in skim milk obtained by allowing milk to stand. Here we have not a definite space through which the globules of fat THEORY OF CREAM SEPARATION. 259 must pass, as in the cream separator, where the layer of milk is always of constant thickness; the space is determined by the depth of the layer of milk set. The formula 2 br* Cc RS v= oe] may be transformed into k : t = —, where & is a constant. r Taking the diameter of the largest globules as 0°01 mm. and the smallest as 0:0016 mm., we calculate that the smallest globules will take about fifty times as long to pass through a given space as the largest; the author deduces from his experiments that the largest fat globules move at the rate of 15 mm. per hour. If we assume that the total weight of fat globules of any size, is equal to the total weight of fat globules of any other size, in an ordinary cream tube we may expect roughly the following figures :— In 5 hours about 35 per cent. of total fat will be found in the cream. » LO ,, >, 65 » ” ” ie i 9 = ” 24 ” ” 89 ” ” ” ” while from three to four days should elapse before the whole of the fat is found in the cream. From the equation Vk. 4 x (de = dyg ot? Cc Y= it will be readily seen that if the density of the fat varies the time will be considerably affected. The density of solid fat at 60° F. (15°5° C.) is about 0°93; the density of liquid fat is about 0-92 at the same temperature; and, as has been shown by the author and 8. O. Richmond, it is highly probable that the solidi- fication of the fat is a process which takes time. The difference between the specific gravity of milk serum and milk fat is also accentuated at temperatures above 60° F.; it is probable that when milk is rapidly cooled, the fat globules do not so easily attain the lower temperature as the serum. It would appear, theoretically, that there is a considerable advantage in setting milk for cream immediately after milking, and that the fat globules will rise at a much more rapid rate than if the milk be cooled and kept for some time. The experiments of Babcock completely substantiate this view; he finds that delaying the setting for even a short time materially affects the percentage of fat in the skim milk. 260 THE CHEMICAL CONTROL OF THE DAIRY. Composition of Skim Milk.—Skim milk differs practically from whole milk in the percentage of fat. In milk from which the cream has been removed by skimming very wide variations are found in the percentage of fat; it varies from 0°4 per cent. to over 2 per cent. Much lower percentages are found in separ- ated milk, and the limits, 0-05 per cent. to 0°3 per cent., are very rarely overstepped. By the removal of the fat the percentage of other solid constituents are slightly raised in amount ; this is caused by the constituents which were contained in 100 parts being left in about 964 parts, by the removal of 3} parts of fat. The following is the average composition of well-prepared separated milk :— Water, F ‘ 3 . . : . 90-48 per cent. Fat, . z c a é : - 012 53 Milk-sugar, . ‘ i ‘ : : . 488 ,, Casein, " 5 : : P ; 322 ix Albumin, . ‘ . : : . 042 ~~ ,, Ash, . : : z . . ‘ . 0-78 Control of Separators —The most important point in the control of separators is the estimation of the fat left in the separ- ated milk. A separator leaving a proportion of fat appreciably higher than that deduced from the formula given above is working badly, and the cause should be at once investigated. It is ime portant that the speed be properly maintained, that the milk be at the right temperature, and that the exit tubes be not clogged up; the chemist should make a practice of visiting the separators daily while they are running and of checking the speed and temperature of the milk. At least one sample of separated milk should be tested from each ‘“‘run” of the separ- ator; these samples should be taken from the skim outflow tube, at some period of the run, preferably not immediately after starting. A further means of controlling the separators is to compare the total weight of the fat in the cream, separated milk, and the milk left in the drum after separating, with the total weight of the fat in the milk separated. This is done by weighing each product, multiplying the weight by the percentage of fat and dividing by 100. The total weight of fat in the cream and separated milk should be nearly equal to that in the milk, the difference representing loss in separating; the average loss should not amount to more than 2 per cent. of the total fat in the milk. Separator Slime.—After running a separator a viscous sub- stance is found on the inside of the drum. It is usually of a dirty white colour ; but if the milk contains much solid impurity, CONTROL OF SEPARATORS. 261 as happens most frequently in the winter, it may be distinctly brown. This by no means consists, as is often considered, of dirt and cow-dung, though it naturally contains these impurities if present in the milk. Microscopical examination shows it to contain— 1. Inorganic impurities—‘.e., dust gathered during transport, and earthy matters due to uncleanliness. 2. Vegetable matters derived from the dust of the food given to the cattle—e.g., bark of hay, fine particles of cake, etc.; in many cases portions of leaves with stomata developed may be identified. Other portions of the vegetable matter have the cell walls considerably disintegrated ; these have probably passed through the alimentary tract of the cow, and indicate the presence of cow-dung. 3. Substances derived from the cow; hairs are often found ; much epithelium from the udder of the cow, and possibly also from the hands of the milkers; and empty sacs (gland cells), which form a very large portion of the slime. (If the cow was in ill-health, mucus, blood, and pus may be present.) Micro-organisms are very numerous; should the cows be afflicted with tuberculosis of the udder, Bacillus tuberculosis may he found here. The following composition is assigned to separator slime by the author and by Fleischmann, respectively :— Author, Fleischmann. Per cent. Per cent. Water, . 8 . é O62 67:3 Fat, . 050 V1 Casein (or analogous body) 5 22 (approx.) 25-9 Milk-sugar, : F OS 2] Other organic matter, : c T75 x Ash, , 3-01 3°6 It is doubtful whether the substance returned as casein is wholly this body; it is undoubtedly a mixture of several pro- teins, including Storch’s mucoid protein. The following is the composition of the ash :— Total ash, . , : . 3-01 per cent. Soluble ash, 7 0-166 ,, Insoluble ash, ‘ ‘ 2544 ,, consisting of Silica, : 0-171 per cent. Iron oxide and alumina, 0-012 - Lime, ‘ ‘ 0-654 ey Magnesia, : W225, Alkalies, . ‘ 0559, Phosphoric anhydride, é : « 1233 262 THE CHEMICAL CONTROL OF THE DAIRY. There are 0°675 equivalent of lime and 0°325 equivalent of magnesia to 1°506 equivalents of phosphoric anhydride, showing that the insoluble ash consists chiefly of (Ca, Mg) (Na, K) PO, like the insoluble ash of milk. The quantity of separator slime amounts to about 0°04 part to 100 parts of milk separated, and varies within comparatively narrow limits—0O-02 to 0-08—unless the milk is very dirty, when it may even reach 0°15; in a sample where the last figure was reached the slime was brown and very gritty. It has been argued that the removal of the slime purifies the milk to such an extent that its keeping qualities are enhanced. This opinion is probably founded on observations of the number of microbes contained in the slime ; but though a greater relative quantity are found than in the milk, the numbers left in the cream and separated milk are not appreciably diminished. Fig. 35.—Diagrammatic Section of Separators. Practice has, however, shown that a mixture of cream and separated milk in their original proportions keeps no better than the milk from which they were separated. Micro-organisms are so small that their separation, unless carried with much larger solid particles, would be almost im- possible under the conditions of the separation of cream; in addition, many of them have a density less than that of milk serum. The author found Top, . . 197,000 colonies per c.c. Growth on gelatine at 22° rapid, about 20 per cent. liquefied. Middle, . 5,000 re Bottom, . 194,000 e Growth on gelatine slow, none liquefied. CONTROL OF SEPARATORS. 263 Attempts have been made to remove the impurities in milk by filtration; straining through a fine wire sieve and through Fig. 36.—Section of Alfa-Laval Hand Separator. A, Holding pins for bowl; B, bowl nut; C, cream screw; D, tubular shaft; #, top disc; F, alfa discs; G, bowl hood; H, bowl ring; J, driving wheel shaft ; J, bushing for driving wheel shaft; A, driving wheel; L, guard ring; Jf, crank lever; NV, oil tube for worm wheel ; O, guard; P, worm wheel shaft; @, bushing for worm wheel shaft; R, worm wheel ; 8, frame ; u, supply can; 5, milk faucet; ¢, bracket ; d, tloat; e, regulating cover; f, regulating tube; g, cream cover; h, skim milk cover; *, lubricator for top-bearing ; j, lubricator fixture ; k, top-bearing brass; /, top-bearing bushing; m, top-bearing spring ; n, stop screw; 0, worm screw; r, lubricator for bottom screw; s, lubricator fixture; ¢, lower bushing; «, steel point ; +, nut for bottom screw ; x, bottom screw; y, waste oil catcher. 264 THE CHEMICAL CONTROL OF THE DAIRY. fine muslin or swandown is always practised in dairies; this removes the grosser impurities—t.e., hairs, large vegetable fibres, ete.—but the quantity removed in this way does not exceed 0-0025 per cent. In Denmark and Germany, and in a few dairies in England, filtration through layers of gravel and sand is practised, though the method appears now to be dying out; this method, which adds considerably to the labour of handling the milk, owing to the necessity of washing the gravel and sand with caustic soda, followed by water, sterilising, and drying, fails to remove appreciably more from the milk than simple straining or upward filtration through muslin or swans down. Another method which is considerably used is filtration through a thin layer of cotton wool; this method is fairly efficient, especi- ally if practised as soon as possible after milking, and before the particles of dirt have had time to disintegrate and yield their soluble matters and micro-organisms to the milk; a special advantage of this method is that the cotton wool is very cheap, and it is impossible to wash it, and, therefore, it is thrown away and not used a second time. The separator is also used as a cleaner for milk; for this purpose the separated milk and cream are either all made to come out of one outlet or they are mixed immediately after separation. This method is, of course, perfectly efficient in removing solid impurities, but it necessitates the milk being warmed and after- wards cooled, and makes the milk very frothy, and may even lead to incipient churning. Cream—Composition.—The name cream is given to the layer which rises to the surface when milk is allowed to stand. This layer consists essentially of the fat globules, together with a proportion of the aqueous portion of milk (Fig. 37). Qualitatively, it has the same composition as milk; quantita- tively, it contains a higher proportion of fat, the other consti- tuents being correspondingly depressed. It is by many accepted as a fact that cream contains a larger proportion of solids not fat to water than the milk from which it was derived; and various explanations of this have been put forward. Thus a membrane round each fat globule has been alleged to exist by some (e.g., Storch and Béchamp) ; others have considered that the proteins are concentrated in the aqueous layer formed round each globule by surface tension. The author’s experiments have indicated that the ratio of solids not fat to water in cream is the same as that in milk, and Weibull and Smith and Leonard have confirmed this conclusion. It is true that in some cases a distinctly higher ratio has been found, but it has been noticed that in these cases ample opportunity for CREAM. 265 evaporation of the water has been afforded, either by leaving the cream on the surface of the milk for some length of time in a dry atmosphere, or by pasteurising it, without any precautions to prevent evaporation ; indeed, evidence of evaporation has been obtained by noting the quantity of cream before and after pasteurising. In cases where precautions have been taken to prevent evaporation, no evidence of a higher ratio has been obtained. In the following analyses (Table LXIV.) the solids not fat have been calculated by dividing the percentage of water by 100 and multiplying by 10-2 (except in No. 2 where 10:0, and No. 9 where 10°4 has been used), this being the average ratio Fig. 37.—Cream. in the milk from which these creams were prepared. The calcu- lated ash is 54, of the calculated solids not fat :— TABLE LXIV.—Composition oF CREAM. z z | | Solids not! Solids not Diff. LP ae as Diff. i | No. | Total ia Fat. [| Fat, Cale. | Cal | | 2 | h Per cent, | Per cent. | ‘Percent Per vent. | (iy Bese 683 | 690 | O07 9 OT 057 | / 2 | 87:59 | G14 6-24 —ul0 | 0:52 0352 | | 3. ; 50:92 | 5:02 | 501 —O01l O42 © 0-42 | P40 (5505 | 465 | 4-58) —0-:06 0°38 | 0:38 fee. ' 5. | 65-18 477 0 4057 —0-2) 039 038 —O-01 | , G& : 5597 | 447 449 9 0-02. 038 | 037° —0-01 | 7. 4) 56:37 4-40 4:45 0-05 033 0-37 —oul | s. 57-99 417 . 4:28 —Ov9 | Ort] 0-36 U5 | 0, 68-18 | 3-30 3:31 —OUL O28 | 0-28 cia: 266 THE CHEMICAL CONTROL OF THE DAIRY. In cream No. 1 the proteins were also calculated, and found to be 2°60 per cent., while the figure calculated on the assumption that they are 37°8 per cent. of the solids not fat, as in milk, is 2°58 per cent. The statement that cream contains a higher proportion of solids not fat to water than milk, though to some extent due to the evaporation of water which takes place, is probably also due to the methods of analysis employed. Thus it is known that when butter fat is heated in contact with air for some hours an increase of weight is noticed. As cream contains from 25 to 50 per cent. of fat, an apparent increment in the total solids of from 0:1 to 0°3 per cent. may be noticed. If the fat be esti- mated by a method which avoids a long heating, and the solids not fat deduced by difference, the increment will swell the amount. of solids not fat. Many analyses of the fat in cream have been made by methods which do not completely extract the fat; the solids not fat are thus still further increased. The following analyses show the composition of creams :— Thick Cream. Thin Cream, Water, 39-37 per cent. 63-94 per cent. Fat, . 56-09 5 29-29 3 Sugar, . 2:29 a 3:47 Be Protein, 4 Z 1:57 o 2-76 re Ash, 0:38 35 0-54 5 99-70 100-00 s The following table will show the proportion of milk-sugar, protein, and ash to 100 parts of water contained in cream com- pared with those contained in milk and separated milk (see Mean Composition on pp. 150 and 260) :— | Cream. | Milk. | Separated Milk. Per cent. Per cent. | Per cent. | Milk-sugar, . : 5:55 5:45 5°39 Protein, ‘ 4-05 3:90 4:02 Ash, : ‘ 0-88 0-86 0:86 It is impossible to give an average composition of cream, as the variation of the fat is enormous; the author has obtained cream containing 9 per cent. of fat as a minimum, and 68 per cent., and even slightly more, as a maximum. As milk has been known to contain as much as 12 per cent. of fat (from Jersey cows), it follows that no sharp distinction between milk and cream can be drawn. Attempts have been made to fix a CREAM. 267 standard for cream, but without success. Thus it has been pro- posed that any product containing less than 25 per cent. of fat should not be recognised as cream; the absurdity of this is shown by the fact that, while much of the cream sold in London contains between 40 and 50 per cent. of fat, being prepared by a separator, cream made by the Swartz process but rarely comes up to the standard proposed. Ash.—It has been alleged that the ash of cream is practically free from chlorides; this, however, is not in the author’s experi- ence correct; the ash of cream differs in no respect from that of milk, The following is the composition of the ash of cream according to Fleischmann :— Potash, . . . $ » 28°381 a cent. Soda, ‘ ‘ : . : 8679 Lime, ‘ é ‘ é P . 23-411 i Magnesia, . : . . 3340 ‘8 Tron oxide, : 4 ‘ 2915 #8 Phosphoric anhy ar ide, , a « 21-735 8 Chlorine, . ‘ * F . 14°895 ay 103356 7 Less oxygen equivalent to chlorine, = 3356 - 100-W00 3 Density.—The percentage of fat varies inversely as the density of the cream. A formula connecting the two can be deduced from the formula expressing the relation between specific gravity, fat, and total solids in milk. T = 02625 7 +12 F, Assuming that the solids not fat (S) are in the ratio to the water as 10-4 : 100, 100 - F oe Tos = § ie 100 - F so sig P=F+ loe1s = ~ 166 substituting in the formula 100 4 O815 a ae @ 10-615 Tr ey 3123 F = 100 — 2-756 F = 32-0 — 0-892 268 THE CHEMICAL CONTROL OF THE DAIRY. It is impossible to test the specific gravity of a cream con- taining more than 30 per cent. of fat with a hydrometer direct ; but if it is diluted with an equal weight of separated milk the hydrometer can be used as with a thinner cream. To calculate the specific gravity of a thick cream from that of a mixture with an equal weight of separated milk, the following formula may be used :— c = specific gravity of cream. 33 », of separated milk. m 3 a of mixture. Cream containing 25 per cent. of fat decreases in specific gravity 0°00027 or 0°27° for each 1° F. above 60° F. Table LXV. shows the results obtained by calculating the fat from the specific gravity. TABLE LXV.—CatcunaTion oF Fat in CREAM. Specifie Gravity. Vat Estimated. Fat Calculated. — - - ; Per cent. Per cent. rz L-0035 29°2 28°9 1:0057 27°3 26°9 } 0070 26-2 25'8 10085 24-8 24°5 10099 240 24:1 1 0110 224 22°3 10125 214 211 10130 20°8 20°6 10210 13°3 13°7 SES Seine erens aa: or Sheciac Gravity | Specie Gravity | yap Bstimated. | Fat Calculated. a fil eacainye _! fame Per cent. Per cent. 1:0367 1:0053 555 54:7 1-0367 10041 57:7 56°3 1 0364 10081 49'S 49-0 The specific gravity of cream is affected by the state in which the fat globules exist; if they are in the solid state, the specific gravity will be very appreciably higher than if liquid. The formula given above assumes that they are solid; if, however, the cream has been separated at a temperature above the melting point of the fat, the globules are liquefied, and do not at once assume the solid state on cooling. For this reason the method CREAM. 269 of calculating the fat from the specific gravity is liable to give at times very discordant results. These figures show that, though the estimation of the specific gravity of a cream is scarcely exact enough to serve as a means. of analysis, it is a useful corroborative figure. Considering the sources of error the agreement is very good, and serves as a further proof that cream does not contain a larger proportion of solids not fat to water than milk. Vieth finds that cream containing 40 per cent. fat has, at a temperature of 175° F., a specific gravity of 0°960, and gives the following table :— Cream containing 30 °/, | 40 °/, | 50 °/, Fat. | en Pea ae | | Gives at 185° F. asp. gr., 0-971 , 0°956 OvEI Tn er 0-975, 0-960 0-945, » 165" 4, gy . 0-979 0-964 0-949 A sample of froth taken from the surface of cream running from a Burmeister and Wain separator had the following com- position :— Water, . ‘ : 48-41 per cent. Fat, ; : ; . 4544 ,, Milk-sugar, 4 i z . 4:86 ay Protein, . 5 ‘ ‘ f 1-89 Ash, x ‘ : , . . 0-40 It does not differ in its chemical composition from cream somewhat concentrated by evaporation. The froth, for this. reason, always contains more fat than the cream. Clotted Cream, or cream prepared by the system practised in Devonshire and Cornwall, has been examined regularly in the Aylesbury Dairy Company’s laboratory since 1886. The following are the average results, together with the maxima and minima found :— | Water. | Fat. Ash. Solids not Fat. | Per cent. Per cent. Per vent. | Per cent. Average, . 34-26 58-16 0-60 | 7-52 Maximum, . 44-84 71:37 LIT | 11:70 ; Minimum, ‘ 21-08 44-29 0-42 ; 5-03 | It is seen that the ratio of solids not fat to water is very much higher in clotted cream than in milk, due to the evaporation. which takes place from the surface during heating. 270 THE CHEMICAL CONTROL OF THE DAIRY. Roughly speaking, the ratio of solids not fat to water is double the average ratio in milk. The ratio of ash to solids not fat is very nearly the same in clotted cream as in milk; it is, however, slightly lower. This is partly, if not entirely, due to the fact that on heating milk certain salts of calcium, probably chiefly citrate, are deposited, leaving a smaller proportion in the milk and also in the cream derived from it. The Thickness of Cream.—The thickness is the factor by which cream is usually judged when used for direct consumption. This can be quantitatively estimated by the method generally employed for the determination of “‘ viscosity ”’—7.e., noting the time taken for a given volume of cream to flow through a tube of constant size. The viscosity of a liquid depends on the internal friction—i.e., the friction of molecules passing each other; the viscosity or internal friction of cream is not quite of the same order as that of a homogeneous liquid; in the latter case, the molecules are of equal size (or nearly so), and very small in comparison with the diameter of the tube through which the liquid passes. The viscosity of cream depends on two factors—the internal friction of the very small molecules of the milk serum, and the friction between the comparatively large fat globules. As the fat globules have an appreciable size compared to the size of the tube, we cannot expect the laws to be of the same kind as those governing the viscosity of a liquid composed of molecules of infinitely small size. The actual and relative size of the globules will also have considerable influence; thus if we have two creams identical in chemical composition, in one of which the relative size of fat globules is much larger than in the other, the “‘ viscosities ” will differ. It is not possible to compare the thickness of cream by making a determination of the percentage of fat in a sample. It is possible, however, to make a comparison of cream which contain globules of relatively the same size. For instance, if cream be ‘diluted with the separated milk, which is practically free from fat, the thickness can be deduced by making determinations of fat. The law connecting thickness or viscosity and amount of fat is expressed by the following empirical formula— Var’, where V=the viscosity, F,=the volume of fat in 100 volumes of cream, and z=a factor dependent on the units in which the viscosity is ex- pressed, and on the relative size of fat globules. THE THICKNESS OF CREAM. 271 The volume of fat in 100 volumes of cream may be calculated from the percentage of fat (by weight) by the following formula— p = 107527 F x 100 | “OL F +965 This is true at a temperature of 60° F. (15°5° C.), and may be used without appreciable error at other temperatures. The following two series will illustrate the exactitude with which the formula agrees :— TABLE LXVI. Senres I, P t. Fat | Per cent. Fat es Cale. Cale. Cale. | by Weight. by Volume. Viscosity. Viscosity. “h oo ee Arig 62:9 65°4 151°6 lors 65 3 625 60°3 629 88-0 90°3 G28 60-2 i 57°7 (0°3 552 52°7 60°6 38-0 | 52°6 [53 212 O14 553 52°6 Series II 61-4 63-95 170 165'8 64-05 615 53:7 564 obs 33°94 501 53°4 46:0 48°7 9°8 96 45:9 452 The agreement is within the limits of experimental error. Instead of the formula given above, which includes a calcula- tion of the percentage by volume of fat, the following approxi- mate formula may be used— V = 100" where F is the percentage of fat by weight. For smal] differ- ences the results by the two formule agree sufficiently well. A practical method for the dilution of cream to constant thickness may be founded upon the above formula. To take the viscosity of a cream, a 10 c.c. pipette with a fairly wide opening, marked with distinct lines both above and below the bulb, may be employed; it should be surrounded by a water-jacket made of glass to ensure a constant temperature; and the end should not project far beyond the jacket. Care must be taken that its position is always vertical during the test; this may usually be ensured by clamping the jacket firmly in position and fixing the pipette by rubber corks. The position should be tested by a plumb line, made of cotton, passing through the pipette. The ‘‘ viscosity ”’ of the cream is represented by the number of 272 THE CHEMICAL CONTROL OF THE DAIRY. seconds that the cream in the pipette takes to flow from the mark above the bulb to that below, which can be determined with sufficient accuracy by any watch with a seconds hand, though it is preferable to use a stop watch. Care must be taken that the cream is free from lumps, or solid particles, and it may advantageously be filtered through muslin. The pipette should be clean and dry, and the cream should be allowed to remain in the pipette a few minutes before making the test, in order to ensure that its temperature is that of the jacket. It will be found in practice that it is better to use water of the mean daily temperature in the jacket than water at any constant temperature, because a purchaser is not in the habit of reducing cream to a temperature of (say) 60° F. before passing judgment on its thickness. At the same time that the viscosity is estimated a determina- tion of the fat should be made by one of the methods recom- mended (pp. 138, 227, and 237). The relation between viscosity and fat can be calculated by the formula given above, which may be expressed, for practical use, as 107-527 F log (log V) = 3 log (es) + log x, Or, log (log V) = 2-7 log F + log z,. A standard viscosity must be fixed, which evidently must be determined by each operator to suit his apparatus, and the con- ditions under which it is necessary to work; the value of log x or log x, having been found from the determination of viscosity and fat, the percentage of fat which will correspond to the stan- dard viscosity can readily be calculated. If a be the percentage of fat found in the cream, and b the percentage of fat which will be contained in the cream of standard viscosity, the cream may be reduced to standard viscosity by adding to each 100 parts 100 (2) parts of separated milk, or 100 ( t — “) parts of milk containing / per cent. of fat. The figure 3°5 may generally be used for / without appreciable error. As an example the following result may be taken :— V =170 log v = 2-23045 log (log v) = log 2-23045 = 0-34839 F = 61-4 107527 F O-11 F + 96-5 log 63-95 = 1-80584, and 3 log 63-95 = 5:41752 then 5:41751 = 034839 + 5-06913. ll = 63-95 ARTIFICIAL THICKENING OF CREAM. 273 Now let the standard viscosity be 25. log 25 = 1-39794, and log 139794 = 014550 therefore, 5-21463 = 0-14550 + 5-06913 now 5:21463 = 3 x 1-73821 = 3 log 54-7, and the percentage of fat in cream reduced to standard viscosity is 52 0 per cent. by weight, or 54°7 per cent. by volume. Now a= 61°4, and b= 52:0 chen 100 (235) 164: that is, to each 100 parts of cream 19°4 parts of milk must be added to reduce it to standard thickness. By the formula V = 107¥”" the percentage of fat calculated in the cream of standard viscosity is 61°7, which is a figure sufficiently close for practical purposes. Artificial Thickening of Cream.— Cream has been arti- ficially thickened by the addition of various foreign substances ; thus, gelatine, isinglass, and substances of like nature have been employed, but without great success, as the cream thus treated has an appearance markedly different from that of genuine cream. The following method, due to Stokes, may be applied to detect gelatine in cream :—To 10 grammes (approximately) of cream add 25 c.c. of water and 2 c.c. of Wiley’s acid mercuric nitrate solution (p. 90), and shake well; filter through a dry filter. In the presence of much gelatine the filtrate cannot be obtained clear, and it is not essential that it should be so. On adding a saturated aqueous solution of picric acid a yellow precipitate is formed in the presence of gelatine ; if the quantity of gelatine be but small, the precipitate does not form at once, but the solution becomes turbid, and precipitates after a lapse of some minutes. Starch, which has been gelatinised by heating, has also been used; this, of course, is readily detected by the characteristic blue coloration given with tincture of iodine. Of comparatively recent introduction is “ viscogen,’’ which is a solution of lime in cane-sugar syrup; the addition of a small amount of this substance has a remarkable effect in increasing the thickness of cream. It is sold under various fancy names. Its presence may be detected by testing the cream by one of the methods (p. 105) for the detection of cane sugar; the amount of ash will be raised, and the ratio of lime to phosphoric acid in the ash will be higher than 17:23. It is usually added in quan- tities of about 0°5 per cent., and this amount increases the solids not fat by about 0-2 per cent. of cane sugar, the ash by about 0-04 per cent., and raises the ratio of lime to phosphoric acid to about 1: 1. As homogenised cream will not whip, it is not uncommon to add gelatine, agar, or gum tragacanth for the purpose of making 274 THE CHEMICAL CONTROL OF THE DAIRY. a fairly permanent foam when the cream is whipped. Of these, gum tragacanth added in the proportion of 0'1 per cent. is the most effective. A careful microscopic examination of the cream after the addition of a little iodine solution will reveal the presence of particles of gum tragacanth, in which starch granules can be detected. Agar, which has also been used as a thickening agent, gives Cayaux’s resorcinol test for cane sugar, but not any of the other tests. Homogenised Milk.—In the equations given on p. 256 the fat globules have been considered as being free from any con- densed layer; this is not the case, as the surface energy of small globules condenses round them a layer of serum, which may, for physical considerations, be included in the globule; this will decrease the value of ds — df, retard, and in extreme cases stop, the rising of very small globules. In the case of the globules of cows’ milk the influence of the layer is sufficiently small, though not absolutely negligible, to be left out of consideration. When, however, the globules of fat are reduced to a diameter below that of the smallest naturally occurring globules it becomes of importance,’ and the rate of rising of cream is much less than that indicated by the formule. By forcing milk, heated to such a temperature * that surface energy is reduced to a minimum, while chemical change in the milk is prevented, under a high: pressure through very small openings, the fat globules are reduced to a very small size. The condensed layer bears such a relation to the globule that the cream rises with extreme slowness, and practically speaking remains mixed with the milk. This process is termed homo- genising. Owing to the fact that the condensed layer is held so firm by the great surface energy of small particles, it is im- possible to churn milk or cream that has been homogenised ; as the effective diameter of the globules is increased by the condensed layer, homogenised milk and, especially, cream are thicker for the same percentage of fat than fresh milk or cream. Surface energy varies considerably with temperature, and con- sequently the thickness of the layer; for this reason the thick- ness of homogenised cream varies more with temperature than the thickness of ordinary cream. Homogenised cream can neither be churned nor whipped. * The temperature should not exceed 60° C., as the mechanical work done in forcing the milk through small openings is partly converted into heat, which raises the temperature of the milk some degrees. CHAPTER V. BIOLOGICAL AND SANITARY MATTERS. ConTENTS.—The Decomposition of Milk—Micro-organisms—Action on * Milk—Pathogenic Organisms—Conveyance of Disease—Water Supply —Inspection of Source—Analysis of Water—Bacteriological Examin- ation — Summary of Sanitary Precautions — Products formed from Milk by Micro-organisms. The Decomposition of Milk—Mlicro-organisms.—The decom- position of milk is due to the action of micro-organisms. The description of their life-history, and the means of separating and identifying them belong to the science of Bacteriology. The following slight sketch will, however, be found of use to the dairy chemist :— Classification.—Micro-organisms belong to the vegetable kingdom, and are classed among the fungi; they are divided into Schizomycetes or fission-fungi. Saccharomycetes or yeasts. Hyphomycetes or moulds. The Schizomycetes are again divided into families according to their shape and mode of growth :— Bacteria; short rod-like forms forming no spores. Biedli ; rod-like forms forming spores. Spirilla ; curved rod-like forms. Aicrococe? ; round forms occurring aingly. e. Diplococes ; 5 4 Pe dou Staphylococe:; ,, ., in bunches. Slreplococe!; yy .. growing in chains. Surcine ¢ » in groups. > ’ Leuconostoc ; thread-like forms. Cladothriz ; branching forms. The distinction between these forms is by no means absolutely defined; thus many species forming spores with difficulty or only under certain conditions, which were formerly classed as Bacteria, ave now called Bacilli. Some organisms grow as micrococci, streptococci, spirilla, and leuconostoc. Action on Milk. For the purpose of the dairy chemist micro-organisms may be classed according to their action on milk, as follows :—— 276 BIOLOGICAL AND SANITARY MATTERS. Those acting on milk-sugar (a) producing lactic acid ; (b) butyric acid ; ” (c) fe alcohol. ; Those acting on proteins (a) curdling milk without acidity and not dissolving the curd ; (b) curdling milk without acidity and after- wards dissolving the curd ; (c) peptonising the proteins without curd- ling the milk ; (d) producing evil-smelling sulphur com- pounds. Those producing coloured substances. Those having no action on milk. ; We may also place in another class those which are pathogenic. Milk is a model food for micro-organisms, for it contains in an assimilable form all those compounds which are necessary for the sustenance of life. It has been shown by experiment that it is possible, though not easy, to obtain milk which is quite free from micro-organisms. It is necessary, however, to reject the first portions drawn, as these contain micro-organisms which have found their way down the duct of the teat. The last portions are practically sterile, and it is highly probable the few organisms found are due to accidental contamination of the milk during its passage from the teat into the sterilised bottle into which it was drawn. Prac- tically speaking, all the organisms found in milk fall in after milking; in certain'diseases—e.g., tuberculosis of the udder— the Bacillus of tuberculosis is not derived from external sources, but passes from the diseased tissue into the milk. Generally speaking, micro-organisms only develop between the temperatures of 4° C. (39° F.) and 50° C. (122° F.); each organism has an oplomum temperature—z.e., one at which its development and ‘action are most rapid; this varies from 12° C. (53°6° F.) to 40° C. (104° F.) in different species; the optimum temperature of pathogenic organisms and of most of those acting on milk is about blood-heat. Among other conditions which regulate their development are (1) the amount of acid present in the milk—thus most of the organisms which produce lactic acid are paralysed in their functions when more than about 1 per cent. has been produced ; and (2) the presence or absence of oxygen. Some organisms can do without oxygen, and are called anderobic ; others require it for their life processes, and are designated derobic. : Growth of Bacteria in Pasteurised and Unpasteurised Milk.—L. A. Rogers has made experiments on the average acidity of raw and pasteurised milk, and the number of bacteria present at different times. BACTERIA IN MILK. 277 The following are his results :— TABLE LXVII. Average Increase in Acidity of Milk expressed as per cent. of Lactic Acid. | ; ‘Treatment. | Lactic Acid aft actic Acid after et Pasteurised . Pasteurised ser geptataire. | Milkkeptat | yeptae ore, | Mik kept at | Per cent. Per cent. Per cent. Per cent. 0 hours, 0-131 0-134 0-136 0-134 6 ts, a 0-168 0-134 0-152 0-129 | 12 35 0-254 0-127 0-167 0-131 | 24.~—=C«d, 0-449 0-130 0-177 0-129 | 48 si 0-696 0-251 0-233 0-129 | Tae 59 0-711 0-271 0-388 0-130 96, ; oe 0-359 0-497 0-132 ; Average Number of Bacteria per Cubic Centimetre in all Samples under each Treatment. Description and Treatment of Sample. Number of Bacteria after the lapse of — Raw Milk Pasteurised Raw Milk Pasteurised | wept atuer ui, | SUM Reptat | sent stor, | “ie Repeat 0 hours, | 13,522,331 245 —-17,640,428 245 6 ee 74,142,857 426) 31,457,833 308 12 ne _ 247,651,250 6,028 38,406,785 378 24 . | 457,910,714 | 1,501,335 | 124,783,928 1,026 48 oe | 608,079,166 | 320,337,388 | 254,678,542 15,119 72 a5 568,718,500 ,; 236,941,250 | 308,041,666 2,462,492 96 = | 3 975,500,000 | 562,650,000 37,088,456 of Milk. Average Number of Peptonising Bacteria per Cubic Centimetre Number of Bacteria | Description and Treatment of Sample. \ t ! found after a 7 lapse of-— | Raw Milk at Pasteurised ea hae Milk at Pasteurised ! 20" C: Milk at 20°C. orc Milk at 10° C. { | 0 hours, 621,571 i $2,208 | 7 cane) aan 4,905,333 ll 505,333 ll 1 ‘a 1,814,583 188 , 1,518,666 | 9 24 Ow 2,927,857 259,831 5,272,500 | 15 48 4s 700,000 2,411,163 1, 708.750 3,143 (ey 1,375,000 | 31,225,000 | 12,781,250 856,219 ,96 ; - | 32,918,750 | 4,251,219 978 BIOLOGICAL AND SANITARY MATTERS. From these results he draws conclusions as under :— Milk held at 20° C. (68° F.).—In the unheated milk the lactic bacteria increased rapidly, and the milk became acid in about twelve hours. The peptonising bacteria increased in six hours to about 5,000,000 per cubic centimetre, and then decreased slowly. In the heated milk the peptonising bacteria increased rapidly after twelve hours, and the milk was usually curdled in forty- eight hours, with a disagreeable taste and odour. Occasionally lactic bacteria survived pasteurisation and multiplied rapidly after twenty-four hours, completely inhibiting the peptonising bacteria. Milk held at 10° C. (50° F.).—In unheated milk the growth of the bacteria and the consequent curdling of the milk was much retarded. The average milk did not contain sufficient acid to affect the taste until it was over forty-eight hours old. The proportion of peptonising to lactic bacteria was greater than at the higher temperature, and the taste of the milk occasion- ally showed the influence of the former. In the pasteurised milk the bacteria increased very slowly, and in nearly every case the milk was unchanged in taste and appearance ninety-six hours after pasteurisation. In only two of fourteen cases was there a marked increase of peptonising bacteria. The predominating bacteria were species having little or no effect on milk. The lactic bacteria inhibited the development of the pepton- ising bacteria only when they had developed sufficient acid to render the milk unfit for use. It seems probable that the acid had a distinct inhibitory action on the proteolytic enzymes of the peptonising bacteria. Distribution of Micro-organisms on Separating.— When milk is separated by centrifugal force, both the cream and the separator slime contain a larger proportion of organisms than the original milk: this is partly due to the organisms being carried down mechanically, but partly also to an actual separation taking place, as the following experiment will show :-— A sample of separated milk was run for fifteen hours in a centri- fugal machine at the rate of 1,000 revolutions per minute. Culti- vations on gelatine were made from the top portion, the middle, ‘and the bottom. The results were, after eight days at 22° :— Colonies per goli5 C-C. Remarks. Top, . . 197 Growth rapid, about 20 per cent. liquefied. Middle, . 5 ae Bottom, . 194 Growth slow, none liquefied. This appears to show that, while some micro-organisms have LACTIC AND BUTYRIC FERMENTATIONS. 279 a density greater than 1°036, others have a less density. The top cultivation was made from the portion immediately under- neath the thin layer of cream, so that it is not probable that they were carried up by the cream. Lactic Fermentation.—The most commonly observed effect of the action of micro-organisms is the souring of milk. This is due to a numerous class of organisms, chiefly bacteria and bacilli, which convert the milk-sugar into lactic acid. The chemical equation for this change usually given is Cy2H 20,1 + OH, = 4C;H,0;. The change, however, never proceeds in this delightfully simple manner, certain quantities of carbon dioxide and often alcohol being always produced; by keeping up a free supply of oxygen a very large proportion of carbon dioxide can be obtained. Some lactic ferments give an amount of lactic acid agreeing approxi- mately with the above equation ; others produce notable amounts of alcohol and other products. Other organisms, again, produce very small quantities of lactic acid and large amounts of other substances. Hueppe has studied this class of organisms minutely and has described many species; few of these form spores and are destroyed with comparative ease by heat ; generally speaking, their optimum temperature is about 35° C. (97° F.). A number of organisms, grouped under the designation Bacillus of Massol, have been recently studied, which produce very large quantities of lactic acid (up to 3 per cent.). They do not ferment cane sugar. These all form chains of long rods, which stain often unequally by Gram. Butyric Fermentation.—When this takes place the milk coagulates without the development of acidity, but the milk becomes alkaline; a bitter taste is acquired, the precipitated casein is redissolved, and butyric acid is formed; an unpleasant smell is usually developed. This fermentation, which does not readily occur if lactic acid is developed, appears to be also caused by many micro-organisms, which attack both milk-sugar and casein. When this fermentation takes place, the solid portion of the milk is reduced to a very much greater extent than by the lactic fermentation. There is another butyric fermentation which takes place with development of a very high acidity, and in which the lactic acid produced by the lactic ferments is converted into butyric acid. Large quantities of gases—carbon dioxide and hydrogen —are produced, and other volatile acids, acetic and, more rarely, propionic, are produced at the same time. This fermentation does not develop till the milk has stood for some time, and appears 280 BIOLOGICAL AND SANITARY MATTERS. to be anaerobic. Some organisms produce acetic or propionic acids as well as butyric. : Alcoholic Fermentation.—This does not readily occur in milk. As already mentioned, small quantities of alcohol are produced as bye-products by some organisms; ordinary yeasts, Saccharomyces cervisia, etc., do not cause fermentation of milk- sugar, but one species of Saccharomyces is known which converts the bulk of the milk-sugar into alcohol; this is found in kephir grains, together with organisms producing lactic acid and others acting on the proteins. ; Curdling Organisms.—These organisms act on the casein by the secretion of an enzyme, which resembles rennet in its action; these are usually bacilli, which readily form spores and are difficult to kill by heating. Organisms which Curdle without Acidity and Redissolve the Curd.—This class is a very large one; the organisms act by the secretion of enzymes having proteolytic functions analogous to pepsin and trypsin. Many of the organisms producing butyric acid belong to this class; among the most noticeable of which are the hay- and potato-bacilli. Organisms which Peptonise the Milk without Curdling. —tThis class is probably more numerous than has been described ; they also act by the secretion of a proteolytic enzyme. It is rare to find milk which shows their characteristic behaviour, as there are generally other organisms present which curdle the milk. When cultivated in sterile milk, no action is at first apparent, but the milk gradually becomes more and more trans- parent till it assumes an appearance like a liquid jelly. The author has separated an organism of this class from “* mazoum,”’ an Armenian preparation. Organisms acting on the Proteins with Production of Evil-smelling Sulphur Compounds.—There is a class of strict anderobes which peptonise the milk with some curdling, and produce volatile sulphur compounds, including sulphuretted hydrogen. These form spores, which are very difficult to destroy, and are the most frequent cause of trouble in so-called sterilised milk, in which the sterilisation has not been efficient. Golding and Feilmann have described a class of organisms that, in the presence of small quantities of copper, dissolved from an imperfectly tinned copper milk cooler, produced an objectionable flavour in milk. Chromogenic Organisms—Milk “out of Condition.??— Several organisms have the property of producing coloured substances; these, and one or two other classes, are the chief causes of milk being “ out of condition.” Blue Milk.—Sometimes the formation of dark blue patches CHROMOGENIC: ORGANISMS. 281 on the surface of milk, having the appearance of a drop of blue- black ink which has fallen in, is noticed. This is due to an organism called B. syncyanus or B. cyanogenus ; when cultivated alone a grey colour is produced, which turns an intense blue on the addition of acids; the blue colour is only noticed if the milk be sour with lactic acid. Red Milk.—This is occasionally due to the action of micro- organisms; it is usual to ascribe the formation of red milk to Micrococcus prodigiosus, which forms an intense blood-red sub- stance, but it is doubtful whether this organism is always the cause. The colour is often of a pinkish tinge, and is due to the pink yeast, Micrococcus rosaceus, Bacillus iactis erythrogenes, or Sarcina rosea. The organism causing a red colour varies according to the district, and only one organism is usually found in any district. A red colour in milk may be due to the presence of madder in the food eaten by the cattle, but far more frequently arises from the presence of blood; this is produced by a diseased state of the udder, but far more frequently by some slight local damage, through a kick or a blow resulting in the breaking of a small blood-vessel in the udder. Yellow Milk.—An organism which curdles milk and redissolves the curd to form a yellow liquid has been described as Bacillus synzanthus ; there are probably several organisms which produce a yellow colour; all seem to have proteolytic functions. Yellow milk is very rare, though it is very common to see dirty vessels which have contained milk become quite yellow. Green milk, violet milk, and bitter milk have been found to be produced by micro-organisms. Bitter principles may be derived from the food of the cattle, and some, though not all, of the butyric ferments give rise to a bitter taste. Peptones produced from casein may also be the cause of bitterness. Ropy Milk.—Milk occasionally, instead of remaining liquid, becomes a thick slimy mass; if a glass rod is dipped into milk which has become ropy and withdrawn, a portion of the milk adheres and can be drawn out in long threads. Sometimes this action is confined to the cream on the surface, but with other organisms the whole milk becomes ropy. The organisms which produce ropy milk do not grow well at a low temperature, and it frequently happens that milk at a dairy goes ropy in the summer, is free from this trouble in the winter, and becomes ropy again in the spring. When milk is found to become coloured, or to be ropy. the dairy, and all vessels used for milk, should be submitted to a thorough disinfection, which will remove the cause. The Bacillus of Massol tends to produce a sour, ropy milk. 282 BIOLOGICAL AND SANITARY MATTERS. Soapy Milk.—After a few hours milk has been known to acquire a fishy odour, alkaline reaction, and soapy taste. Herz regards this as due to a disease of the cow, and has found that such samples have a high specific gravity; Weigmann has iden- tified an organism, which he also found in the straw used as a litter, which gave a soapy taste to milk. Moulds.—White mould (Qidium lactis) is very commonly found on sour milk; it forms a tough white skin on the surface, which is entirely formed by the hyphe and mycelium of the mould. A brown mould, which penetrates down into the milk, is sometimes observed. Green moulds, Penicillium glaucum, and other species, also grow on milk, and are the colouring agents of some cheeses—e.g., Roquefort and Gorgonzola. Camenbert. cheese is ripened by moulds. Pathogenic Organisms—Conveyance of Disease through Milk.—If, as already mentioned, a cow is suffering from tuber- culosis of the udder, the bacillus passes into the milk. It has been proved that the organism retains its toxic properties, and to this cause the bulk of cases of infantile tubercular intestinal disease can be traced. Tuberculosis is by no means an uncommon disease in cows. Evidence was given before the Royal Com- mission on Tuberculosis that in Copenhagen and Berlin, where all animals before being slaughtered are systematically examined by veterinary experts, the percentage of oxen and cows affected with tuberculosis was 17°7 and 15:1 per cent. respectively of the total number examined. In many herds the number exceeds this; on one farm as many as 80 per cent. of the cattle were affected. In a large proportion of the cattle the disease did not affect the milk-producing organs, and in these the milk did not contain the tubercle bacillus; in a very noticeable proportion the milk was, however, affected. As there is no certainty that the disease may not spread to the udder, even though the bacillus be not detected in the milk, the presence of tuberculosis in a cow should always be taken as a sign of danger. On the Continent and in America this subject has received much more attention than in this country, but now that the teport of the Royal Commission on Tuberculosis is completed, it may be expected that legislation will follow, which will mini- mise this cause of infection. An obvious means of preventing infection by tuberculosis is to remove the diseased cattle, and only use healthy cows as the source of milk supply. As the tubercle bacillus is comparatively easily destroyed by heat, pasteurisation of milk may be resorted to to destroy the organisms; keeping the milk for a quarter of an hour at 70° C. (162° F.) will practically remove the source of PATHOGENIC ORGANISMS. 283 infection. Another, but less satisfactory means, is to mix the milk with that of healthy cows and trust to Providence for the presence of sufficient lactic acid organisms to destroy the tubercle bacilli; even if they are not destroyed, they are sometimes so diluted that they have no toxic effect on healthy adults, though children and persons weakened by disease or predisposed by heredity to consumption may be affected. Other diseases—pleuro-pneumonia, foot and mouth disease, and scarlatina (or an analogous skin disease)—may be derived from the cattle. These are much less common than tuberculosis and less insidious, as the symptoms can be detected with com- parative ease in the cows. Practically speaking, tuberculosis is the only disease which needs to be guarded against by systematic veterinary inspection. Conveyance of Disease through Contamination of the Milk.—The labours of the late Ernest Hart in collecting statis- tics have conclusively shown that typhoid, cholera, scarlet fever, and diphtheria can be conveyed through milk. There are practically two causes: (1) the occurrence of the disease in the milkers and those handling the milk, and their families; and (2) the presence of the organisms to which the malady is due in water used for “‘ cleansing ”’ the utensils or for adulterating the milk. The epidemics of scarlet fever and diphtheria which have been spread through milk have almost all been due to the milk being handled, shortly after milking, by those either affected with the disease, or living in the same house with sufferers. The remedy is, of course, obvious; a rule should be made in every dairy that all employés who feel unwell should absent themselves from their work, and pay an immediate visit to a medical man; if any members of their families be ill, medical advice should be simi- larly obtained; and if the disease be infectious, the em ployé must be at once suspended from duty, and not allowed to go near the dairy. It is found in practice that this regulation can be carried out (1) By the employer providing for the services of a medical man. (2) By the payment of full wages to any employé who is suffering from infectious disease, and suspended from duty. (3) By a distinct understarding that the breaking of the regulation by an employé means instant dismissal without notice. Water - borne Diseases.—Typhoid and cholera, which are essentially water-borne diseases, have, in the majority of cases investigated, been due to the use of contaminated water for the cleansing (sic) of dairy utensils; the small amount of water left on the sides of the vessel is sufficient, if the water contains virulent germs, to infect the milk; even more so does this occur if the 284 BIOLOGICAL AND SANITARY MATTERS. practice of washing out the dairy vessels with a little water alter milking, and adding this to the milk, prevails. The precautions against this form of infection are also obvious, though more difficult to carry out in practice than those mentioned above. Water Supply. A water supply which is not contaminated, nor liable to con- tamination, and a good system of sanitation are necessary. Before milk is supplied from a farm or dairy the water supply must be rigidly investigated. The investigation may be con- veniently divided into three parts. (1) Inspection of source. (2) Chemical analysis. (3) Bacteriological examination. Inspection of Source. The following sources of supply are almost always satis- factory :— (1) Deep artesian borings. (2) Deep wells passing through an impervious stratum—e.g., clay. (3) Springs fed by an uninhabited watershed—e.g., springs in the sides of hills. Public water supplies, mountain rills, and wells sunk in open ground remote from habitations are very frequently—but by no means always—of a satisfactory nature. On the other hand, shallow wells near dwellings, ponds, small brooks, and wells in pervious strata—e.g., gravels—are usually unsatisfactory. The following points must be considered to be highly unsatis- factory :—The proximity of privies, cowsheds, etc. ; the trend of the lands from habitations to the source; faulty conditions of the sides of a well (otherwise satisfactory), which may allow surface drainage to enter; and, except in the case of springs on the sides of uninhabited hills, a marked diminution of the supply after drought, and increase after rain. It is advisable to ascertain the geological formation, and whether artificial fertilisers are much used in the vicinity; if this is done to a large extent, some of the chemical evidence may be discounted. Chemical Analysis. Taking of Samples.—aAt least half a gallon of water must be taken for the analysis; a “‘ Winchester quart” bottle is con- venient for this purpose. The first portions—say, 10 to 20 WATER ANALYSIS. 285 gallons—should invariably be rejected, and the bottle should be rinsed with the water, filled nearly full, care being taken to avoid undue aération, and despatched to the laboratory as quickly as possible. The following data should be obtained :— Colour.—This should be observed in a layer at least 12 inches in length; a yellowish-green tint is always suspicious, and points to sewage contamination ; a brownish or brownish-yellow indicates vegetable products, not necessarily harmful, but usually undesirable. A nearly colourless water, with a faint blue or bluish-green tinge, is shown by most good waters. Smell.—A_ small wide-necked bottle is half filled with the water, which is warmed to about 60° C. (140° F.); the water is shaken, the stopper removed, and the smell noted. Foul smells show badly polluted waters; a peculiar sweetish unpleasant odour is often given by waters containing sewage. Few waters are absolutely devoid of smell when tested thus; for instance, waters from the Oxford clay sometimes smell of petroleum, and a smell of pines is not uncommon in wooded districts. Analytical Figures—Total Solids.—250 c.c. (or 100 c.c.) are evaporated in a weighed basin on the water-bath, and dried to constant weight at 150° C. Loss on Ignition.—The residue is ignited over a very small flame; the smell of the vapours given off should be noted, as polluted waters often give an unpleasant smell. Much blacken- ing indicates a large amount of organic matter; if nitrates are abundant, red nitrous fumes may be observed. Chlorine.—100 c.c. of the water are placed in a white porcelain basin, 1 ¢.c. of a 1 per cent. solution of pure potassium chromate added, and silver nitrate (4°7887 grammes AgNO, per litre) run in till a faint reddish colour is produced. The quantity of silver nitrate required to give a similar tint with 100 c.c. of distilled water is subtracted, and the difference represents milligrammes of chlorine, or parts of chlorine per 100,000 of water. Free and Albuminoid Ammonia.—250 c.c. of water are placed in a stoppered Wiirtz flask, to the delivery tube of which a condenser is connected; the condenser must be a good one, and drawn out at the end, so that the diameter of the opening does not exceed 1 millimetre. If the water be distinctly alkaline to methyl orange, nothing need be added; but if not, a little freshly ignited sodium carbonate must be dropped in. A flame is placed under the flask, and about 125 c.c. of the water distilled and collected in a stoppered bottle. So soon as the flame is placed under the flask, about 250 c.c. of distilled water are placed in a flask and brought to the boil (or nearly so); the flask is removed to the bench, 10 grammes of caustic soda added, and, 286 BIOLOGICAL AND SANITARY MATTERS. when dissolution of this is complete, about half a gramme of potassium permanganate dropped in. This solution of alkaline permanganate is boiled, while the distillation is proceeding, at such a rate, that its bulk, when 125 c.c. have distilled from the flask, should be just about sufficient to make up the original volume. The alkaline permanganate solution is added to the Wiirtz flask; and a further 125 c.c. are distilled off, and collected in a second stoppered bottle. The first bottle contains the free (or saline) ammonia, and the second the albuminoid (or organic) ammonia. The contents of the bottles are well mixed, and 50 c.c. of each are placed in a Nessler cylinder, 2 c.c. of Nessler solution added, and the tint in each of them matched by placing a known volume of standard ammonium chloride solution in a Nessler cylinder, making up to 50 c.c. with distilled water free from ammonia, adding 2 c.c. of Nessler solution. The waters must be allowed to stand for five or ten minutes before the final comparison is made, as the colour does not develop instantaneously. After a little practice, it will be found easy to make an approxi- mate match of tints at the first trial. It is not necessary to do this exactly. If the cylinder which contains the distillate is of approximately the same depth of shade as the standard, a little may be poured from the darker cylinder till the colours are matched ; the positions of the cylinders should be several times reversed before finally deciding that they are equal, as a shadow may be cast on one cylinder more than the other and make it appear darker than it really is. If the cylinder containing the distillate is the darker, and some of the solution has been poured from it, the calculation is performed as follows :—Let « = the weight of ammonia equal to the amount of standard ammonia solution taken, y = the amount of solution poured out, and z = the total amount in the cylinder; then the weight of ammonia in 50 c.c. of the ° z By from 250 c.c. of water is found by multiplying by the totai volume of the distillate, which should be measured, and dividing by 50. If the cylinder containing the distillate is the lighter, and some of the solution has been poured from the standard, the calculation is slightly different :—Let « = the weight of ammonia equal to the amount of standard ammonia solution taken, y = the amount of standard solution poured out, and z = the total amount in the cylinder containing the standard solution ; then the weight distillate = 7 x , and the amount of ammonia obtained of ammonia in 50 c.c. of the distillate = x x 7 _¥. WATER ANALYSIS. 287 It is very important that the 50 c.c. mark on each Nessler cylinder should be accurately the same height ; unless this is so, the thickness of the layer will not be proportional to the volume. Nessler Solution.—Dissolve 35 grammes of potassium iodide in 100 c.c. of water; next dissolve 17 grammes of mercuric chloride in 300 c.c. of water; reserve a little of the potassium iodide solution and add the mercuric chloride solution to the rest, till a permanent precipitate is formed; then add the remainder of the potassium iodide solution and cautiously drop in mercuric chloride solution, till a faint permanent precipitate is left. Dissolve 160 grammes of potassium hydroxide in water, cool it, and add this solution to the mercury potassium iodide solution and make up to 1 litre. The solution is more sensitive the lower the temperature at which it is prepared, and also if a little more mercuric chloride solution is added. The solution is left to settle and the clear portion decanted for use. Standard Ammonium Chloride Solution.—Weigh out 0°3146 gramme of pure ammonium chloride, and dissolve in 100 c.c. of ammonia-free water; dilute 10 c.c. of this to 1 litre with ammonia-free water for use. 1 ¢.c. = 000001 gramme NH.,. Ammonia-free Water.—Boil ordinary distilled water in a flask to half its bulk and cool in an atmosphere free from ammonia. Nitrie Acid.—Place about 0°01 gramme of diphenylamine in a porcelain basin, add 1 ¢.c. pure sulphuric acid, and mix; run two or three drops of the water down the sides of the basin, so that they will flow over the surface of the acid. In the presence of nitrates a blue colour will be developed. From ihe amount and depth of coloration produced a rough idea of the amount of nitric acid present can be formed, which will be useful in the quantitative estimation. Measure 2 c.c. to 10 c.c. of the water by an exact pipette into 2 porcelain basin, according to the amount indicated by the diphenylamine test, add 1 c.c. of a 2 per cent. solution of sodium salicylate, and evaporate to dryness on the water-bath ; measure also a known volume, usually 2 ¢.c., of the standard potassium nitrate solution into a porcelain basin, add 1 c.c. of a 2 per cent. solution of sodium salicylate, and evaporate to dryness. To each add 1 ¢.c. of sulphuric acid, and heat for five minutes on the water- bath. Dilute to about 20 c.c. with distilled water. make alkaline with caustic soda solution (30 per cent.), and dilute to 50 c.c. Compare the colours produced in Nessler cylinders and calculate in the same manner as directed under Free and albuminoid ammonia. Standard Potassium Nitrate Solution.—Dissolve 1°85 grammes of pure potassium nitrate in | litre of water; dilute 30 c.c. to 1 litre for use. 1 c¢.c. = 000003 gramme N.O.. 288 BIOLOGICAL AND SANITARY MATTERS. If the chlorine be high, the method just described may give results below the truth, and the following method may be used :— Place about 200 c.c. of water in a wide mouthed stoppered bottle with three pieces of copper-zinc couple. Leave for twenty-four hours in a warm place, or longer if a reaction for nitrites is ob- tained; then take 100 c.c. and distil off 50 c.c. of this, after making alkaline with sodium carbonate. Estimate the ammonia in the 50 c.c. (or an aliquot part, 5 or 10 ¢.c. diluted to 50 c.c. are often sufficient) in the manner previously directed. The ammonia found (less the free ammonia present) multiplied by 3-2 will give the nitric acid (as N,O,). Preparation of Copper-Zine Couple.—Cut a number of pieces of sheet zinc 4 x 1 inch, and immerse them successively in 2 per cent. caustic soda solution, distilled water, 2 per cent. sulphuric acid solution, and distilled water, keeping them for about two minutes in each solution and agitating them. Place them in 3 per cent. solution of crystallised copper sulphate till a firm black deposit is obtained; rinse them well in distilled water, without undue handling; and preserve in a stoppered bottle filled with strong alcohol. Nitrites—Dissolve about 0°05 gramme of meta-phenylene- diamine in dilute sulphuric acid (10 c.c.); add 10 c.c. of water and allow the mixture to stand. A brownish-pink coloration is produced, if nitrites be present. Oxygen absorbed from Permanganate.—Clean out a stoppered bottle with chromic acid and rinse well with distilled water. Take 250 c.c. of water, add 10 c.c. of dilute sulphuric acid and 10 c.c. of standard potassium permanganate solution, mix, and keep at a temperature of about 80° F. (27°4° C.) for four hours. Add a crystal of potassium iodide and titrate with standard sodium thiosulphate solution till only a faint yellow colour remains; then add a little starch solution and continue the titration till the blue colour disappears. To 250 c.c. of distilled water add 10 c.c. of sulphuric acid and 10 ¢.c. of potas- sium permanganate; and titrate with standard sodium thio- sulphate solution (2 grammes per litre).* The difference between the amounts of sodium thiosulphate solution used, divided by the amount of sodium thiosulphate used for the sulphuric acid, potassium permanganate and distilled water, and multiplied by 0°001 will give the weight of oxygen absorbed by 250 c.c. of water. Dilute Sulphuric Acid.—Mix 100 c.c. of pure sulphuric acid cautiously with 300 ¢.c. of water, cool to 80° F., and add * The addition of a little, say 0-05 gramme, of sodium salicylate will render this solution permanent. WATER ANALYSIS, 289 so much potassium permanganate solution that a faint pink tinge remains after four hours. Standard Potassium Permanganate Solution.—Dissolve 0395 gramme of pure potassium permanganate in 1 litre of dis- tilled water. 1 ¢.c. = 00001 gramme oxygen. Starch Solution.—Make an emulsion of 0°5 gramme of starch in 2 ¢.c. of water and add this to 50 ¢.c. of boiling water. Boil for five minutes and cool. Phosphates.—Dissolve the ignited residue from the total solid estimation in a little dilute nitric acid; evaporate the solution to dryness in a porcelain dish, and take up with | c.c. of dilute nitric acid, filter the solution, and wash the filter paper with very small amounts of water, Add to the filtrate. which should not exceed 2 or 3 ¢.c., an equal bulk of ammonium molyb- date solution and warm to 60° C. (140° F.). A yellow coloration is called a ‘very faint trace’ of phosphates. and a distinct precipitate a“ very heavy trace.” Ammonium Molybdate Solution.—Mix 14 c.c. of strong ammonia (sp. gr. 880) with 28 ¢.c. of water, and add 10 grammes of molybdie acid and stir till all is dissolved. Add this solution, slowly and with constant stirring, to 125 c.c. of nitric acid (sp. av. 1°2); stand the solution in a warm place for a few days and decant the clear solution for use. A slight deposit may form on keeping. Hardness.—To 100 c.c. of the water add 5 drops of methyl- orange solution, and titrate with a hydrochloric acid solution a till the tint is the same as that of 100 c.c. of distilled water to ¢ h which five drops of methyl orange and 0-2 ¢.c. of Ti acid: have heen added. Subtract O-2 cc. from the reading. and the re- mainder multiplied by 2°5 will give the alkalinity or temporary hardness in parts per 100,000. Transfer this solution to a porcelam dish, and boil down to half its bulk ; pour it in toa 100 ¢.c. flask, rinsing the basin with well-boiled distilled water, and add a measured volume (10 c.c.. : N : 15 c.c.. or 20 v.c.), according to the hardness. of a i solution of soda, half carbonate and half hydroxide: make up to near the mark with well-boiled distilled water. cork up, and cool; when cold make up to the mark. and allow it to stand at least one hour, Filter through a drv filter. and collect an aliquot ; ar aN Bs Ankers portion (sav 90 ¢.c¢.), and titrate with a hydrochloric acid till equal in tint to that of the distilled water to which methyl orange 19 290 BIOLOGICAL AND SANITARY MATTERS. and 0:2 c.c. of a acid have been added; calculate the number of ¢.c. used to the total volume (7.c., if 90 c.c. have been taken, divide by 0°9), and subtract 0-2 c.c. Titrate in the same manner the volume of 0 soda added, and the difference between the two results multiplied by 2°5 will give the total hardness as parts of calcium carbonate per 100,000. The amount of soda solution added should be such that at least half the quantity of acid is required to neutralise the filtrate. The permanent hardness is obtained by subtracting the tem- porary hardness from the total hardness. Interpretation of Results of Water Analysis——Good waters contain, generally speaking :— Total solids, 20 to 40 parts per 100,000. Chlorine, . . ; lto 2 we - Free ammonia, . not more than 0-001 = 5 Albuminoid ammonia, a >» 0:010 5 5 Nitric acid, i Oto 2 ats a Nitrites, ‘ ‘ none. They absorb less than 0-1 part per 100,000 of oxygen, and are practically free from phosphates. The total solids may be higher than the limits named, in chalk waters and in mineral waters. A high chlorine content may be due to beds of rock salt—e.g., in waters from the new red sandstone—or to admixture with salt derived from the sea (near the coast) ; it is, however, usually due to sewage. Deep well waters often contain large amounts of free ammonia : and water which has passed through iron pipes may also contain free ammonia and nitrites. A high albumimoid ammonia is usually very undesirable, though not conclusive of pollution by sewage; pools into which lead leaves fall may give rise to high albuminoid ammonia. Nitric acid is a most reliable datum; any amount above 3 or 4 parts per 100,000 is certainly due to pollution. The presence of nitrites is always unfavourable, except when the water has passed through iron pipes, and in chalk waters. The amount of oxygen absorbed does not give much infor- mation as to whether a water is polluted with sewage; high figures are often due to vegetable matter. The proportion cf oxygen absorbed to albuminoid ammonia is often a useful datum. Where vegetable contamination has taken place the oxygen absorbed is ten times (or more) the albuminoid ammonia; in polluted waters it is usually less. BACTERIOLOGICAL EXAMINATION. 291 The presence of phosphates is usually regarded as an un- favourable symptom; this may, however, be due to the use of artificial fertilisers; the nitric acid may be increased from this cause. If waters known to be pure from the same district and from the same geological formation can be obtained, the water can be compared with them; any marked increase in the figures found must be regarded as evidence of pollution. By this means evidence of contamination is often obtained which would be difficult, or almost impossible, to acquire from chemical analysis alone. It must be remembered in comparing waters with a “ district standard ’’ that in the autumn the figures for free and albuminoid ammonia, nitric acid, and oxygen absorbed usually are slightly higher than at other times of the year. For further information on the subject works on ~ Water Analysis’? must be consulted. It must be borne in mind that the judging of water supplies is not a subject that can be learnt from books entirely, but that prolonged experience is necessary to properly interpret the results obtained. Bacteriological Examinations, A very simple cxamination is all that is usually necessary. A sample of the water for bacteriological examination must be taken in a sterilised bottle; a six-ounce stoppered bottle is plugged with cotton wool, and the stopper is wrapped in cotton wool and tied to the neck; the bottle is sterilised for three hours at a temperature of 150° C. (350° F.). The sample is best taken directly after the sample for analysis has been obtained ; the plug of cotton wool is removed and the bottle filled with water without being rinsed ; then the stopper is quickly removed from its cotton wool wrapping and inserted in the bottle. The examination must be commenced with as little delay as possible ; and, if the sample has to be forwarded by post or rail, it should be packed in ice. The examination usually consists in making a velatine culti- vation at 22° C. and a search for microbes of intestinal origin. Preparation of Nutrient Media—Nutrient (relatine.—120 grammes of velatine (Coignet’s Extra Gold Label) are dissolved in I litre of water on the water-bath; 5 grammes of Liebiy’s extract of meat and 10 grammes of peptone are added, and dissolved by further heating ; the whites and shells of two egys, stirred up together to make an intimate mixture are next added, and the heating on the water-bath continued till the liquid ts 292 BIOLOGICAL AND SANITARY MATTERS. cleared. Five c.c. is titrated after dilution with 5 c.c. of water with - alkali solution, and from the figure thus obtained the quantity of a strong caustic soda solution necessary to reduce the acidity to 15 ¢.c., N acid per litre is calculated, and added. The liquid is now filtered, the filter being kept warm, and the clear filtrate is ready for use. Portions of 10 ¢.c. are placed in test tubes which have been previously plugged with cotton wool and sterilised by heating for half an hour at 150° C. (350° F.). The nutrient gelatine in these tubes is sterilised by heating to 100° C. (212° F.) in steam for fifteen minutes on four successive days, or by heating in an autoclave to 120° C. for fifteen minutes. M‘Conkey’s Bile-Salt Glucose Peptone Medium.—Weigh out 20 grammes of Witte’s peptone, and dissolve in about 300 c.c. of warm tap water, add 5 grammes sodium tauro-cholate, and stir well till dissolved, adding a little more water to wash down the sides of the vessel; a porcelain double saucepan, in the outside portion of which water is kept boiling, serves admirably for the preparation of media. Add 5 grammes of glucose and water to make altogether 900 c.c., and heat till the solution is clear; fiter, and to the clear filtrate add 100 c.c. strong neutral litmus solution. Prepare also some media of twice and some of three times the above strength. Plug with cotton wool, and sterilise a number of test tubes, each containing a small 2-inch x }-inch tube (Durham tube) ; these tubes should be of different sizes, some of them holding about 180 c.c., others about 50 ¢.c., and the remainder about 30 c.c. The largest tubes should be marked at 150 c.c., and the medium-sized ones at 20 c.c. To the largest tubes add 50 c.c. of the triple strength medium, to the next size 10 c.c. of double strength medium, and to the others 10 c.c. of the ordinary medium. Sterilise these as directed for the gelatine. ; M‘Conkey’s Bile-Salt Lactose Peptone Neutral Red Agar—To 1 litre of tap water, 20 grammes Witte’s peptone, 5 grammes of peptone, 5 grammes of lactose, 15 grammes of powdered agar are added, and dissolved by heating; the solution is then centri- fuged in wide tubes till as clear as possible, care being taken that the temperature does not fall so low that the agar solidifies. Pour off the clear liquid, add sufficient of a strong solution of neutral red to colour the whole a deep red colour, place quantities of 10 c.c. in plugged test tubes, and sterilise. Allow the agar to solidify so that a slantine surface is obtained, : Peptone Water.—This contains 1 per cent. Witte’s peptone and 0°5 per cent. salt; the solution is heated till clear, filtered, BACTERIOLOGICAL EXAMINATION. 293 and quantities of about 1 c.c. placed in Durham tubes, which are plugged with cotton wool, and sterilised. Sugar Media—The sugars used are glucose, lactose, and cane sugar; other carbohydrates, such as dulcitol, adonitol, and inulin, may be also used, but the three sugars give a fairly good distinction between the organisms of intestinal origin. These media are made up, containing 7°5 per cent. gelatine, 2 per cent. peptone, 1 per cent. Lemco, and | per cent. of the sugar; they are heated till clear, filtered, 1 c.c. of 5 per cent. potash solution added, and the media tinted blue with litmus. Quantities of about 1 ¢.c. are placed in Durham tubes, five of the small tubes being held together by an india-rubber band, and contained in a 3-inch x l-inch plugged test tube. They are sterilised as usual. Milk Tubes.—Plugged test tubes, each containing 10 c.c. of separated milk, are sterilised. It is a convenience to plug tubes containing the various media with different coloured cotton wool; this saves labelling, and minimises the chance of error. The use of different coloured cotton wool also serves to distinguish different quantities of water taken. Prepare also a number of test tubes, each containing 9 c.c. of distilled water; plug these with cotton wool: and _sterilise. The tubes containing nutrient media and sterilised water must be covered with a rubber cap to prevent evaporation. Procedure.—Sterilise a pipette delivering 1 ¢.c. by heating to 150° GC. (350° F.); the pipette is best sterilised in a test tube plugged with cotton wool. As soon as this is cool, open the bottle containing the sample, and take out 1 ¢.c. Add this to one of the tubes contaiming sterilised water and replace the plug immediately. Take out another 1 c.c. and add this to a tube of nutrient gelatine, which should have been previously liquefied and allowed to cool to 27° C. (80 F.). Pour into a sterilised Petri dish. With another sterilised 1 ¢.c. prpette add | c.c. of the mixture of water with sterilised water to a tube of nutrient gelatine, which has been previously liquefied by heating and cooled to about 27° C. (80° F.), and pour into a Petri dish. The Petri dishes Lactic acid, ‘ A O47 : Proteins, s 4 7 2-56 +s Fat, . ! ; 205 ,, Sugar, : , ‘ : 4:38 Koumiss has the advantage of being a food and a stimulant at the same time; and is, for this reason, often prescribed by the medical faculty in cases of disease (r.7., gastritis) when no other food can be retained. Kephir.—This is a preparation of a similar nature to koumiss and is produced from milk by means of kephir grains. The following is the composition of kephir according to various authorities :— TABLE LXX. | Konig (mean), . Hammarsten. Gu, rine : ' Per cent. Per cent. Percent. | Water, . 91-21 88-915 9-09 Alcohol, . ‘ ‘ . 0-75 0-720 0-64 1 Lactic acid, : . ‘ 1-02 0-727 O-44 | Fat, ‘ : a 1-44 3-088 P82 : Sugar, . : ; 2-41 2-685 1-87 | Casein, . ‘ ‘ 2-83 2-904 2-90 Albumin, ‘ 3 ‘ 0:36 O186 0-07 : Proteoses, : : 0-30 0-067 O45 Ash, : ‘ : - 0-68 0-708 Kephir differs from koumiss chiefly in the comparatively small amount of proteoses it contains, showing that, although the alcoholic and lactic fermentations have taken place. the protein-hydrolytic fermentation is very weak. Struve found in kephir grains :— Water, - 11-21 per cent. Fat, . fe « P 3°99 ‘e Protein, P é i . 31-69 we The author has examined a * kephir powder,’’ which had the following composition :— Water, : : a . . 2-29 per cent. Milk-sugar, f j F 5 . 89-90 34 Other organic matter, - 2 Gs? 4 Sicko ke aa . ee 300 BIOLOGICAL AND SANITARY MATTERS. It appeared to be a mixture of milk-sugar with pulverised kephir grains. Mazoum.—This preparation, lately introduced from Armenia, where it has been made for centuries, has somewhat the appear- ance of clotted cream; on warming, it separates into a liquid whey and an insoluble curd. The author has determined the following figures :—- Fat, : 6-27 per cent. | Casein, 2:56 ,, “Curd. Ash, 004 2 | Organic solids, 5-00 a | Ash, 0-77 ss - Whey. Water, . 3538 7 | There was no evidence of proteoses in the whey. Mazoum appears to have been produced by the lactic fermen- tation of milk enriched with cream: the sample examined was very fresh and protein-hydrolytic fermentation was not appre- ciable. An organism was separated from mazoum which gave colonies rapidly spreading on the surface of gelatine to 1 em. or more in diameter, and which produced a slight putrid smell. This organism, which was a bacillus, slowly peptonised milk without curdling it, and finally transformed it into a semi-transparent liquid jelly. Bulgarian Sour Milk.—This preparation is a thick gela- tinous liquid of pleasant acid taste. It may contain as much as 2} per cent. of lactic acid, and the proteins are hydrolised to a considerable extent. The milk used for its preparation is sometimes concentrated. 301 CHAPTER VI. BUTTER, Cortexts.—Detinition of Butter—Composition—Vheory of Churning— The Proximate Analysis of Butter—The Analysis of Butter Fat— Preparation of the Fat for Analysis—Recapitulation of Properties —Estimation of Volatile Fatty Acids—Saponification Equivalent— Soluble and Insoluble Fatty “Acids—Colour Tests for Adulterants —Behaviour of Butter Fat with Solvents—Iodine and Bromine Absorption—Heat Evolved by Sulphuric Acid—Physical Examination of Butter Fat—Microscopic Examination—Density—Refractive Index —Viscosity-—Melting Point—Detection of Adulteration of Butter— Influence of Keeping on Butter—Buttermilk—Chemical Control of Churning Operations. Definition Butter is the substance produced by churning milk or cream, during which process the fat globules coalesce to form granules; when freshly churned, butter has the appear- ance of a fine granular mass; but, after being worked, this assumes a structure homogeneous to the naked eye. Composition.—Storch gives the following mean composition to butter :— TABLE LXXI—Composirion or Burrer. From Fresh Cream. | From Ripened Cream. Per cent. Per cent. Fat, 2 ‘ 83°75 82-07 Water, ‘ 13°03 13°78 Protein, ; F ‘ 0-64 0°84 Milk-sugar, . F ‘ 0°35 0°39 Ash, : i O-4 0°16 Malt, 2 6 2-09 | 1-86 \ He further argues that the milk-sugar must all belong to the buttermilk, which fills the spaces between the fatty portion ; and, from the composition of the buttermilk, calculates the proportion of water, proteins, and ash belonging to this. 302 BUTTER. TABLE LXXII.—Composirion oF BUTTER. From Fresh Cream. From Ripened Cream J Per cent. Per cent. Fat, . F ‘ 83°75 82-97 Buttermilk 6:95 8-49 Water, 6°31 774 Milk-sugar, 0-35 0-39 Protein, 2 ‘: 0°23 0-29 Ash, . 0-06 0-07 Mucoid substances, . 7:21 6-68 Water, , 6:72 6-04 Protein, 41 0-55 Ash, 0-08 0-09 Salt, 2-09 1-86 Proportion of Solids not Fat to Water.—Vieth has shown that in butter the proportion of solids not fat to water remains, so long as no water is added, the same as that in milk— ie., 10 to 100; he gives the following average analyses :— Composition of Different Kinds. gait. | SEs po Water’ Designation. Fat. Water. Curd. Per cent. | Fer cent. | Per cent. | Per cent. | English, . . 2) 8685 |) 11-54 059° Lue 5 French, fresh, . 84°77 13 76 138 3: 0069 | 10 amie 8434 | 1205 | 160 | 2-01 | 13 * German, salt, 85°24 io ae 10 Danish, ,, 83-41 | 1342 130 | 1-87 | 10 Swedish, ,, §2°89 13°75 1°33 | 243 10 | The following analyses by the author show the average com- position of French fresh butter (giving the amount of preserva- tive), and of Australian butter :— atiavati 7 r “d ait, Abhydrous Anhydrous _ Commercial Designation. Fut. Water. Curd. Salt. Borax. Borie Acid. = Hrsselys: Perct. Perct. Perct. Perct. Per ct. Per ct. Per ct. French, fresh, $3°92 14°33 1°36... 0-21 O1S = 06°65 Australian, salt, 84:50 12°70 1:21 1:57 ke = a Table LXXIYV. will give the number of samples in which the water falls between the percentage named. The analyses were mace by Vieth, Schnepel, Boseley, Livett, O'Shaughnessy, and the author in the Aylesbury Dairy Company’s laboratory. * Contained boric acid. WATER IN BUTTER. 303 TABLE LXXIV.—-Vartations or Water IN Burrer. English Butters. Foreign Butters. | Percentages of le kd ei! Water. 1 : 4 i No, ofSamples.' Percentage. | No, of Samples. Percentaxe. | ‘ = edz . aes — =| to 8, 2 03 ; sé “ge i 8, 9; 5 O's 5 O-4 + 10, 14 Oe 13 1-0 | 10,, 11, 26 4-2 5l ae | beg 8 65 10°4 7s 57 | 12°, 13, 154 24-6 115 s+ i 13 ,, 14, 152 29°] 395 29-0 14, 15, 07 18 373 ab 15 ,, 16, | 50 SO, 2M ig. 3 16 ,, 17, pa) 3-4 71 ye } 17 ,, 18, I 4 06 21 15 18 .. 19, 3 Onn | 0-1 19 .. BO. | a) 03 ‘Total, 625 | 8 1,564 The above table contains butters of all kinds—fresh. salt, preserved, unpreserved, fresh from churning, and samples which had been kept for various periods. Variations in Percentages of Water.—The following table (LXXY.) is taken from a paper by Faber on Water in Danish Butter ” :— TABLE LXXV.—Variarioxs or Water IN Burrer (Faber), | | No. of Samples. : Percentage of Total. Percentages of | ba I e2mn sts, Sees ra Water, | | summer, Winter. sinner. Winter, 9 to 10, 1 1 uo Ol i... 16 s Os ord 11 D2, 136 mt) O35 lo 12... 15, 335 13s 1ocs oe 13 ,, 14, AB t 431 ; oo Bp: 14 ,, 15, ae 56200¢« | 257 -91 £9 4 1Oy 287 447 | l4-4 23 0 16 ee b 124 205 ; eld 10-6 Vi aig TS, : 39 We | pee | 49 Is, 19, 13 20 O07 10 Above 19, 4 3 : (12 chee Total, ‘ 2,001 1,930 Average, : 14-0377, lath, 304 BUTTER. Table LX XVI. shows the effect of keeping on the percentage of water contained in the butter; fresh and salt butters, which were all prepared at the Aylesbury Dairy Company, are kept separate. TABLE LXXVI.—Vagiations or WATER IN BUTTERS ON KEEPING. Percentages of the Total Number falling between the Limits Named. zen Gentaaes Fresh Butters. Salt Butters. Less than 12 24 to 48 Less thin 12 24 to 48 10 to 30 hours old. hours old. hours old. hours old. days old. 18 to 19, ae is an ce 17_,, 18, iis 25 ae we 16 ,, 17, 17 int 150 38 Sue 15 ,, 16, 10°3 10°0 925 a1 3°6 14 ,, 15, 31°3 15:0 25°0 12°6 a 13 ,, 14, B28 35:0 25-0 34°1 10°7 12 ,, 13, Q0eF 40°0 75 38:0 28°6 IY .,5, 12, 3:4 sais 13 511 42-9 1 ge 21, wes sien 13 107 9 ,, 10, it \ 36 Average percentage] + 13°79 13°54 14:74 13°33 | 12-00 of water, | | Taking butters from twenty-four to forty-eight hours old to represent commercial butter, it is seen that salt butter contains rather less water than fresh butter. The contrary is usually stated ; but this is not according to the author’s experience. Fresh butter loses its water chiefly by evaporation, and it is seen that this Joss is small: salt butter also loses water by brine running out. It will usually be noticed that salt butter looks wet on being cut, while fresh butter rarely has this appearance. Action of Salt—The action of salt, which is added both to give a flavour and as a preservative, seems to be as follows :—It first dissolves in the buttermilk left in the butter, and forms a strong solution, which curdles the buttermilk, giving an insoluble precipitate of protein matter and a clear whey. The salt solution has a smaller viscosity than the buttermilk; hence a smaller layer is condensed round the particles by surface energy, and there is liquid which is very loosely held in the butter; this eradually runs out, and gives rise to the wet appearance of salt butter. It is noticed that the liquid which runs out, or is squeezed THEORY OF CHURNING. 305 out, of salt butter is always clear and transparent, while the liquid squeezed out of fresh butter is usually milky. By warming to a temperature near the melting point of the fat considerable quantities of water can be mixed with butter. In the preparation of ‘ pickled ’’ butter advantage is taken of this fact to add large amounts of salt by working in warm brine. Butter treated in this way does not lose its water easily, as an emulsion of fat and water is thus produced. Storch has shown that by the action of certain micro-organisms such a condition (of the proteins ?) is produced, that large amounts of water are retained and cannot be worked out. In this case an emulsion is produced, which contains large numbers of very minute water globules. These butters are designated ‘‘ thick,” and are rare in England. Theory of Churning.—Several theories have been put: forward to account for the phenomenon of churning. Thus, Fleisch- mann holds the view that the globules of fat in milk are in a superfused condition, and that churning is simply the phenom- enon of solidification ; with the recognition of the fact that the globules are solid at low temperatures this view is untenable. Soxhlet holds that churning consists in the rupture of a solid membrane, which he believes exists round the fat globules; as the existence of such a membrane is disproved, this view cannot be accepted. Storch attributes churning to the gradual rubbing off of a semi-solid membrane of “‘ mucoid substance,” and this hypothesis has much to recommend it ; the whole of the evidence points to the existence of a layer, which is not solid, round the fat globules. As previously stated, the author cannot reconcile Storch’s theory that this layer consists of ‘‘ mucoid substance ” with known facts ; but it appears very highly probable that there is a layer, the composition of which is for the present purpose immaterial, round each fat globule. As it is improbable that this layer is elastic, the effect of the impact of one fat globule on another will be to squeeze out the layers between them, and bring the globules within the sphere of each other’s attraction. In this way nuclei will be formed, which will, on continued churning, increase in size; as the nuclei get larger and larger, the resistance, owing to fluid friction on their surfaces. will gradually bear a smaller and smaller proportion to the force tending to bring them to the surface. and, at a given moment, the butter will ‘come.’ This theory is in accord with all the known facts. By microscopical examination of cream during churning the formation of nuclei of irregularly shaped masses of fat globules is noticed. As an irregular mass will occupy a greater apparent volume than a sphere, the transformation of spherical globules into irregular nuclei should be attended with 20 306 BUTTER. thickening of the cream, which is in accord with the facts; as the nuclei increase in size, the layer condensed by surface energy round them will rapidly become less, so that the cream will gradually decrease in thickness; this decrease in thickness of the cream should take place later than the increase mentioned above, which is also the case. When the butter is taken from the churn it is in fine grains, which are the nuclei referred to. On working, the fat globules are brought still closer to each other, and the butter is formed into a nearly homogeneous mass; small amounts of liquid are, however, left distributed throughout the mass, and as these Fig. 39.—Churn. liquid globules are very small and contained in a medium which, though solid, is still viscous, they are by surface energy trans- formed into spheres. The microscopical examination of butter shows a number of spherical globules of aqueous liquid in a nearly homogeneous medium consisting of fat; there are, how- ever, many fat globules left, which, by careful examination with little light (best by dark stage illumination), can be made out. The whole of the globules usually seen, which are of all sizes, consist of aqueous liquid; in many cases where the globules are of sufficient size for the surface energy to become small, they cease to be spherical. THEORY OF CHURNING. 307 The reason that butter always does, and must, contain water is that the aqueous liquid present is finely divided, and assumes a spherical condition. It is impossible by pressure from the outside to remove small spheres from a homogeneous medium. It appears certain, from the experiments of Storch on the density of butter, that the density of the fat is the same as that of butter fat in the solid state; it is, therefore, solid in butter. This view is nearly universally accepted. With the recognition of the fact that butter is an approxi- mately homogeneous fatty substance, the reason for its change lig. 40.—Butter Worker. of consistency by alteration of temperature at once becomes apparent. To churn butter of the right consistency it is neces- sary that the fat in the cream shall be of that consistency. As pointed out by the author and 8. O. Richmond, the fat in cream which has been warmed very slowly solidifies. If the cream has been kept at a high temperature, as in summer, it is necessary to churn at a lower temperature than if the cream has been kept at a low temperature, as the effect on the consistency of the fat of cream of cooling for a long time at a fairly low temperature is the same as that of cooling for a shorter time at a lower tem- perature. 308 RUTTER. Temperature of Churning.—The best temperatures for churning are as follows :— Recently separated cream (quick churning), about 8° C. (46-4° F.) Fr (slow a » 18°C. (554° F.) Sour cream, winter, : : ee ici C. (64-4° F.) s summer, ¥ ee FS a OF es 4° F.) If the butter is churned at too high a temperature, it will contain more water than at medium temperatures. Butter churned at very low temperatures also contains more water than at medium temperatures; this appears to be due to the fact that in the one case the fat is too liquid, and in the other too solid, for the maximum effect of squeezing out the watery portion on working to be attained. Butter which is quickly churned by violent impact also has a tendency to contain more water than that churned more slowly. This may be explained by the hypothesis that if the nuclei are quickly formed several globules of fat may coalesce simultaneously and enclose more buttermilk than if they coalesced singly. When the cream churned is very sour the solids not fat may contain precipitated casein; in this case the ratio of solids not fat to water is high. If the temperature at which the butter is churned and worked be too high, very large percentages of water (up to 50 per cent.) may be found; this may be very materially reduced by cooling the butter for several hours and re-working. Various substances—rennet, pepsin, sodium carbonate, etc.— have been used to increase the yield of butter; this effect is attained by increasing the water contained in the butter. An article is sold under the name of “‘ milk blended ’’ butter, which is made by working milk into butter; the water is thereby raised to 22 to 26 per cent., and the solids not fat are correspond- ingly increased. Casein, to which sufficient alkali is added to make it soluble, and often containing a little gelatine, condensed milk, and milk powders are also sometimes added to butter. Preservatives in Butter.—Besides salt, various other sub stances are used as preservatives; the most usual are mixtures of borax and boric acid, though formalin, salicylates, sulphites, fluorides, and potassium nitrate have also been employed. The Proximate Analysis of Butier.—The proximate analysis of butter indicates, not whether the sample is genuine or otherwise, but its condition, and affords some clue as to its mode of pre paration. The usual data to be determined are water, solids not fat, fat, salt, and preservatives. It is also occasionally of interest to determine the actual curd, or the casein, ESTIMATION OF WATER IN BUTTER. 309 Water.—The most important datum is the percentage of water. As the water is not always equally distributed through- out the mass of butter, especially in butters which have been salted, it is necessary to take precautions to obtain a fair sample —a matter of some difficulty. It is not advisable to use a scoop. as water is liable to be squeezed out while forcing it into the lump. Perhaps the fairest way of sampling is to cut the lump into halves, and to take a piece near (not at) one top corner, a second piece in the middle, and a third near the opposite bottom corner. The three pieces should be placed in a wide- mouthed stoppered bottle, melted at as low a temperature as possible, and violently shaken till the mass is nearly solid. If the analysis is to be commenced at once, suitable quantities may be poured out while the butter is still in a semi-liquid condition, and weighed as soon as possible. The water by this means is equally distributed throughout the sample, and a small quantity will be representative of the whole sample. In the case of well- made fresh butter the differences in the distribution of water is small, and a single sample taken from any part of the lump will represent with fair accuracy the whole bulk. Where extreme accuracy is not desired, the melting and shaking of samples of fresh butter may be omitted. The water in butter may also be mixed by warming to such a temperature that the butter begins to lose its consistency, and stirring vigorously with a stout glass rod. The mixing of salt butter should not be omitted if accuracy is a desideratum. The following methods are used for the determination of the water :— 1. About 10 grammes are weighed out into a small porcelain basin provided with a glass stirrer. This is placed over a very small flame, or on a sand-bath, and the butter carefully, but vigorously, stirred till all signs of frothing cease. The tem- perature must be so regulated that spirting is avoided, and that the “curd ’’ does not become appreciably browned by the heat. The basin and its contents are, after cooling. weighed ; the loss of weight indicates water. 2. A basin is filled with pumice, which is broken in pieces about the size of a small pea, washed, and ignited ; 2 or 3 grammes of well mixed butter are weighed in, and the basin placed in a drying oven at 100° C. (212° F.), through which a good draught passes. At the expiration of an hour the basin is cooled and weighed, and then replaced in the oven for a further half hour ; weighings are made at the expiration of succeeding half hours till the weight ceases to diminish. The lowest weight obtained is taken as that of the dry butter. The difference between this weight and that of the original butter is taken as water. 310 BUTTER. 3. Four to five grammes of butter are weighed into a wide- mouthed flat-bottomed conical flask, which is placed in a water oven and shaken every ten minutes for the first half hour, after which it is shaken every half hour. At the expiration of four hours it is cooled, weighed, and returned to the bath for another hour; if there be any loss, the drying is continued till an hour’s drying does not cause any diminution of weight. 4. From 2 to 24 grammes of well-mixed butter are weighed into a flat-bottomed basin about 2? inches diameter. This is placed in the water-oven till just melted, and 1 to 14 c.c. of strong alcohol are added; the basin is replaced in the water- oven, and weighed after two hours. The loss represents water. Of the four methods, the first is the most expeditious, and is nearly as accurate as the others ; the second is the most accurate ; the third is the most convenient if solids not fat and salt are also estimated; while the fourth is fairly accurate, rapid, and requires no attention. No one of the four methods has, how- ever, any great advantage over the others. Solids not Fat and Salt.—For the estimation of solids not fat and salt the residue from the determination of water is taken and melted at a low temperature. A solvent for the fat, of which ether is perhaps the best, though chloroform, amy] alcohol, and others may be also used, is poured on, the whole well mixed, and allowed to stand in a warm place till the solvent is quite clear. The solution is carefully decanted and a fresh portion of the solvent poured on the residue, and, when clear, poured off. Four or five successive treatments are sufficient to remove the whole of the fat. With a little practice the operation may be so performed that none of the solids not fat are poured away with the solvent. The residue is placed in the water-oven, and dried to constant weight; the weight represents solids not fat and salt. Salt.—To estimate the salt the residue is treated with hot water and filtered, the filter together with the residue washed, and the filtrate, or an aliquot portion of it, is titrated with a standard silver nitrate solution, using potassium chromate as indicator. It is essential that the solution should be cold before titration, and the silver nitrate solution should be standardised on pure sodium chloride. The strength should not be deduced from the amount of silver nitrate present, as Hazen, and, later, W. G. Young, have pointed out that the amount of silver used is always greater than that theoretically required to combine with the chlorine. From the amount of silver nitrate solution used the weight of salt is readily calculated. It is convenient to make the silver nitrate solution of such strength that 1 c.c. = 0005 gramme of sodium chloride. PRESERVATIVES IN BUTTER. 311 Solids not Fat.—The weight of salt found by titration is subtracted from that of the residue left after the extraction of the fat, and the difference represents the solids not fat. Fat.—The fat is best estimated by subtracting the total of the water, salt, and solids not fat from 100; though the solvent may be evaporated and the fat actually weighed, if desired. Curd.—An estimation of the actual curd present can be made by submitting the residue, left after estimation of the fat, to Kjeldahl’s process for the estimation of nitrogen (p. 124), and multiplying the nitrogen found by 6°38. The milk-sugar may be estimated in a portion of the solution used for the titration of the salt by one of the methods given for the determination of milk-sugar (p. 90). These determinations are rarely required. Casein is estimated by extracting the solids not fat with dilute ammonia till no lumps are left, filtering the solution, and washing the residue; the filtrate is made acid with acetic acid, and the precipitated casein collected én a tared filter or Gooch crucible, and weighed as in the estimation of casein in milk (p. 129). The extraction of the fat, and ignition may be, however, omitted, as the fat has already been extracted, and the amount of ash is so small that it may be neglected without great error. Ash.—In place of an estimation of the salt, an ash deter- mination is often made, and the ash taken as salt. The results are, however, always slightly above those obtained by titration, as butter itself, to which no salt has been added, gives a small ash; preservatives, such as borax, will also swell the weight of the ash. Preservatives.— The preservatives most largely used in butter consist of sodium borates; sulphites and nitrates have also been used, usually in conjunction with borates; fluorides are also employed ; formalin has been recommended, but appears to be rarely used. These should be tested for in the aqueous portion which sinks to the bottom on melting the butter at a low temperature. The reaction with turmeric paper applied to the liquid direct will show the presence of free boric acid. If no reaction or a feeble one be obtained, a little of the liquid may be acidified with very dilute hydrochloric acid, and tested with turmeric paper. A pinkish-brown coloration, turned greenish-black by dilute alkali, will show the presence of boric acid in combination. It will usually be found, if the butter is preserved in this way, that a reaction is obtained from the liquid itself, and a much stronger one after acidifying. The presence of sulphites may almost always be detected by the smell of sulphurous acid developed on acidifying. Nitrates may be found by the diphenylamine test. Fluorides may be tested for as in milk. For the quantitative estimation of preservatives 312 BUTTER. 50 grammes of butter should be placed in a stoppered cylinder, 50 c.c. of chloroform added, and the mixture gently warmed till perfect mixture takes place. A quantity of water, which will, with that present in the butter, make up 50 grammes, is added, and, after shaking, the cylinder is put aside to allow the aqueous portion to separate. Each cubic centimetre of the solution will contain the preservative in 1 gramme of butter. For the estimation of boric acid Thompson’s method is con- venient (p. 85). As butter is practically free from phosphates, the process for their removal may be omitted, and the titration performed on an aliquot portion of the solution which has been made alkaline, evaporated to dryness, and ignited; the ash is extracted with hot water, and titrated first with acid till neutral to methyl-orange, and then with alkali in the presence of glycerol, till neutral to phenolphthalein, the result will be the total boric acid, free and combined. It is, of course, obvious that any of the other methods for the estimation of boric acid (pp. 86 to 88) may be used in place of Thompson’s method. The author and Harrison have devised a rapid method for the estimation of boric acid in butter; 25 grammes of butter are weighed into a beaker, and just melted in the water-oven, 25 c.c. of water are added, and the contents of the beaker well mixed by stirrig; the aqueous portion is allowed to settle; the contents are again mixed, and allowed to settle. 20 c.c. of the lower layer are withdrawn, and the boric acid estimated therein by the method of Miller and the author. The 100 + W 20 of water) will give the percentage of boric acid; the factor 5°65 may be used without great error. The fat may be filtered, and used for the examination of its composition. Pee boric preservative is usually expressed as boric acid, 3B of The Preservatives Committee has recommended :— (D) That the only preservative permitted to be used in butter and margarine be boric acid or mixtures of boric acid and borax, to be used in proportions not exceeding 0°5 per cent. expressed as boric acid. An estimation of the total sulphurous acid may be made by distilling a portion of the liquid with dilute hydrochloric acid. passing the gas evolved into decinormal iodine solution, and titrating with sodium thiosulphate ; 254 parts of iodine convert 64 parts of SO, into sulphuric acid. The gas evolved may also be passed into bromine water, and the sulphuric acid formed weight of boric acid multiplied by (W = percentage ANALYSIS OF BUTTER. 313 estimated as barium sulphate, of which 233°5 parts represent 64 parts of SO,. The solution from which the sulphurous acid has been distilled may be advantageously evaporated to dryness after making alkaline and ignited, and the sulphuric acid esti- mated in this; the sulphuric acid present is probably due to the oxidation of the sulphite. Nitrates may be estimated by one of the methods described under “ Water Analysis.” If much salt be present, the copper- zinc couple method should be employed. Formalin cannot be estimated with any degree of exactitude, as it gradually enters into combination with the proteins present, and only the residue of uncombined formaldehyde, which gives no clue to the original amount, can be determined. If adulteration is suspected, it may be of interest to examine microscopically the residue left after removal of the fat; adulterants, such as starch, mineral matters, etc., which it is alleged have been used, would be thus detected. This form of adulteration is of extreme rarity, but starch is sometimes added to ear-mark margarine. The Interpretation of Results.—The President of the Board of Agriculture has laid down that any butter which con- tains more than 16 per cent. of water shall be presumed. till the contrary is proved, not to be genuine. It is advisable always to calculate the solids not fat and salt, not only as percentages, but also as parts per 100 parts of water present. Table LA XVII, will show the characteristics of various classes of butter :—- TABLE LXXVII. Parts per 100 parts Per cent. Oat: Designation in Class. Water. North of England. | pay ae | Salt. Fresh, unwashed, 12 to 16 8 to 12 none. a » washed, . 12 ,, 16 3 ,, 10 none. \ Almost unknown. Salt, unwashed, | 10 ,, 16 8. ,, 12 5 to 25 | Mild » washed, .| 10,, 16 3 ,, 10 Disney . Pickled, . « | May be high. | Rather low.) 35 ,, 40 | Salt. Mixed with water, Less than 25.! ” ” i Milk blended, . 22 to 26 8 to 12 varies. | The figures given are not intended as absolute limits, but rather as indicating the composition of by far the greater number of samples met with. It is seen that the pickled butters contain 314 BUTTER. a very large amount of salt in proportion to the water present. This fact is of great use in distinguishing them from samples which have been purposely watered. It is frequently stated, even by “experts,” that salt butter contains more water than fresh. Unless the term “ salt butter ” is applied exclusively to pickled butter, this statement is contrary to fact, as it is found that if, after churning, the butter is divided into two parts, one being worked as fresh, and the other imme- diately salted, the percentage of water is almost identical in the two samples; after standing, the salt butter will be found to lose water by running out, while the fresh butter undergoes no such loss. It will be found that salt butter when placed on the market contains on the average less water than fresh butter. A high percentage of water does not appear to have any effect on the keeping qualities of the butter; a large percentage of solids not fat or curd seems to be distinctly inimical to its good preservation. Speaking broadly, butters containing about 133 per cent. of water have the best flavour. When the limits of 12 per cent. on one hand, and 15 per cent. on the other, are passed, a distinct falling-off in quality is usually found. To this rule, however, exceptions are numerous. During very hot weather, if the butter is very soft when taken out of the churn, there is a difficulty in working the water out to a sufficient extent; during very cold weather the butter may be so hard that it cannot be efficiently worked. In both these cases the water may somewhat exceed 16 per cent. An organism has been described which produces changes in the cream which prevent the water from being worked out, but it is fortunately not frequently met with. The Analysis of Butter Fat.—Preparation of the Fat for Analysis. — A portion of the butter is placed in a beaker and melted by exposing to a temperature not exceeding 50° C. (122° F.). The water, with a considerable amount of the other con- stituents, sinks to the bottom, leaving the fat (containing, how- ever, particles of curd in suspension) as an upper layer. If the butter be genuine, fresh, and well made, the melted fat will usually appear transparent; while if it be mixed with butter substitutes, rancid, or churned at a high temperature, or if it has been melted and re-emulsified, the fat frequently has a turbid appearance. The fat, with as little as possible of the other constituents, is poured upon a dry filter, which is kept at a temperature suffi- cient to prevent the fat from solidifying ; the clear fat, separated from all the other constituents of butter, except a trace (0°2 per cent.) of water and lactic acid, if present, is collected in a dry PREPARATION OF BUTTER FAT FOR ANALYSIS. 315 vessel. It is sometimes of importance to prepare the butter free from water. This may be done by shaking it with a little calcium chloride (free from lime) and filtering again. Chatta- way proposes to remove the water by stirring in a number of pellets of filter-paper, which have been dried in the water-oven. The author has found that, as far as the proportions of the vola- tile acids, insoluble acids and saponification equivalent are concerned, the fat is entirely unaffected by this treatment, though certain properties—e.g., rise of temperature with sulphuric acid —are slightly affected, owing to removal of the water. After filtration, the fat is rapidly cooled, so as to prevent partial solidification and to ensure the homogeneous nature of the sample. Stokes’ Fat-clearing Process.—Stokes uses a tube open at both ends (Fig. 41), the smaller and Jower of which is closed with a rubber plug. The lower divisions each represent 1 per cent. For butter ieee it is used thus :— avout The butter is put in it (as the tube stands immersed in boiling water) up to the 15 c¢.c. mark, and when melted the tube is transferred to a centrifuge (800 to 900 revolutions per minutc).* The casein and water are driven into the narrow end and read off. The result is taken as all water. / (This is used to sort out butters which come for water determination, and is not absolutely correct if checked by gravimetric methods.) Into the hot fat a wad of cotton wool is placed, and is slowly forced down by a wire (see Fig. 41), so as to | prevent any cloudy particle from oozing up. The | fat thus obtained (above the pad) is perfectly ‘a clear, practically dry, and ready for use. & Recapitulation of Properties.—The following Fig. 41. recapitulation of the essential differences between stokes’ Butter butter fat and other fats likely to be used as Clearing Tube. substitutes or for adulteration will serve to show the basis of the methods employed in the analysis of butter. Butter fat is characterised by the presence, in con- siderable amount, of glycerides of the fatty acids of low molecular weight. The lowest and most important is butyric acid, but the whole of the members of the series C,H:»,,-1COOH, in which nis an odd number from 3 to 17, are present in butter fat. A considerable amount of acids of the oleic series, of which not much is known, is also present; of this series, the lower members are certainly absent, and the unsaturated acids are of a higher * Gerber disc is quite sufficient. 316 BUTTER. mean molecular weight than the saturated acids: it is probable that oleic acid is the chief representative of the series, and, possibly, higher homologues occur. It is not known with cer- tainty whether acids of other series occur in butter fat. The alcohol present is almost entirely glycerol. The pioneer in butter analysis was Otto Hehner, who demon- strated in 1872 that upwards of 5 per cent. of the fatty acids were volatile, and that the quantity of insoluble fatty acids was very much less than that yielded by nearly all other fats. The bulk of the methods at present in use are the legitimate outcome of Hehner’s work. Perhaps the only method which is not derived from the first investigation of Hehner is that of von Hiibl, who showed that, by the action of an alcoholic solution of iodine and mercuric chloride, a quantitative addition of halogen could be made to unsaturated glycerides, but in the simplification of this method Hehner has had a large share. Estimation of Volatile Fatty Acids. Reichert Process.—Hehner and Angell, after showing that butter contained more butyric acid than was (then) generally supposed, attempted to estimate this by distillation, but finally relinquished the method on account of discordant results, due largely to the bumping of the liquid and the use of too strong an acid. Reichert proposed to saponify 2°5 grammes of butter with caustic soda and alcohol, evaporate off the alcohol, add 50 c.c. of water and 20 c.c. dilute sulphuric acid, and to distil 50 c.c. in a weak current of air. This method, though Reichert himself calls it Hehner’s method, is now known as the Reichert process. He showed that butters took a constant amount of deci-normal alkali for neutralisation, while fats and artificial butters took very small quantities (0°3 ¢.c.), and coco-nut oil took about 3c.c.; he proposed 14°0 c.c. as the mean for genuine butters, and 13°0 c.c. as a limit; he showed also that mixtures of butter and margarine took quantities of x alkali equivalent to the amount of butter they contained. , Meissl proposed to saponify 5 grammes of butter-fat in a flask of about 200 c.c. capacity with 2 grammes of caustic potash and 50 c.c. of 70 per cent. alcohol, and to drive off the alcohol on the water-bath. The resulting soap is dissolved in 100 c.c. of water, and 40 c.c. of dilute sulphuric acid (1 to 10) are added and the solution distilled with a few small pieces of pumice ; 110 c.c. are collected, filtered, and 100 c.c. titrated with deci- normal alkali. In common with Reichert and the earlier experi- menters, he used litmus as an indicator, but the superiority of REICHERT-WOLLNY PROCESS. 317 phenolphthalein for this purpose soon became apparent to many. To the number of cubic centimetres of — alkali used one-tenth is added. 10 Reichert-Wollny Process.—Wollny, in a now classic memoir, studied the errors of the Reichert-Meissl process ; these are :— (1) Error due to the absorption of carbonic acid during the saponification (may amount to + 10 per cent.). (2) Error due to the formation of esters during saponification (may amount to — 8 per cent.). (3) Error due to the formation of esters during the distillation (may amount to — 5 per cent.). Se ‘ “Semel Sem Scar Jo Seme Fig. 42.—Reichert-Wollny Apparatus. (4) Error due to the cohesion of the fatty acids during distil- lation (may in extreme cases amount to — 30 per cent.). (5) Error due to the shape and size of the distilling vessel and to the time of distillation (may vary the results + 5 per cent.). Te avoid these errors he lays down the following method of working :— Five grammes of butter-fat are weighed into a round flask of about 300 ¢.c. capacity, with a neck 2 cm. wide and 7 to 8 cm. long; 2 c.c. of a 50 per cent. soda solution and 10 c.c. of 96 per cent. alcohol are added, and the flask heated for half an hour on the water-bath under a slanting inverted condenser; between the centre and the flask is a T piece, which is closed, the limb being turned upwards. At the expiration of half an hour the 318 BUTTER. limb of the T piece is opened and turned downwards, and the alcohol distilled off during a quarter of an hour; 100 cc. of boiling water are added by the T piece, and the flask heated on the water-bath till the soap is dissolved. The solution is allowed to cool to 50° or 60°, 40 c.c. of dilute sulphuric acid (25 c.c. to a litre; 2 c.c. of soda solution should neutralise about 35 c.c. of this), and two pieces of pumice the size of peas are added. The flask is at once furnished with a cork carrying a tube 0°7 cm. Fig. 43.—Caustic Soda Apparatus. in diameter having, 5 cm. above the cork, a bulb 5 cm. in diameter ; above this the tube is bent at an angle of 120°, and 5 em. further on again at an angle of 120°; this tube is joined to a condenser by an india-rubber tube. The flask is heated by a very small flame till the fatty acids are all melted, and the flame is then turned up and 110 c.c. distilled off in from twenty-eight to thirty-two minutes. The distillate is well mixed, and 100 c.c. are filtered off through a dry filter, 1 ¢.c. of a 0°05 per cent. REICHERT-WOLLNY-POLENSKE PROCESS. 319 solution of phenolphthalein solution in 50 per cent. alcohol added, and the solution titrated with x baryta solution. To the figure thus obtained one-tenth is added, and the amount found by a blank experiment subtracted ; the blank should not exceed 0°33 c.c. In order to render this method more sensitive, if possible, for the detection of small quantities of butter in margarine, Hehner proposed the use of 5 c.c. only of alcohol, saponifying (almost instantaneously) in a closed flask, warming for five minutes with occasional shaking, and driving off the alcohol through a narrow tube in a cork, reduced pressure being applied towards the end, and the addition of 100 c.c. of water which has boiled at least half an hour. He finds the blank figure thus to be less than 0'l c.c., and the same as that given by 100 c.c. of boiled water filtered through a dry filter; other fats and oils give less than 0°06 c.c., and no increase is observed in heating them on the water-bath with soda solution for two hours. To facilitate the melting of the fatty acids, the author proposes lengthening the bulb tube, used by Wollny for distillation, above the bulb to 15 cm. and placing on it a small condenser, through which water is kept running during the melting of the acids, this being removed during distillation; the same results are obtained by the use of this apparatus as by Wollny’s. The Polenske Process.—For the detection of coco-nut oil in butter, Polenske has drawn up very careful directions for the carrying out of the Reichert-Wollny method, and his process includes a determination of the volatile insoluble acids in addition to the estimation of the volatile soluble acids. Alcohol must not be used for the saponification, and glycerol, which was first introduced by Leffmann and Beam, is employed: in fact, so far as the saponification is concerned the method is that of Leffmann and Beam. Five grammes of butter fat are weighed into a 300 c.c. Jena glass flask (Fig. 44), and 20 grammes of glycerol are added, the weight of the glycerol being exact to 0'l gramme; 2 c.c. of 50 per cent. caustic soda solution are added, and the saponification carried out by heating over a naked flame ; at first a considerable amount of frothing takes place, and on continued heating the solution suddenly becomes clear, after which the flask should be set aside to cool slightly, and 100 c.c. of well-boiled distilled water added. A little ignited pumice, which has been powdered and sifted through muslin (Harris recommends that 0°1 gramme should be used), and 40 c.c. of sulphuric acid (25 c.c. per litre) added, and the flask immediately connected by a bulb tube to a condenser. The sulphuric acid solution should be of such 320 BUTTER. strength that 2 c.c. of caustic soda solution should neutralise about 35 c.c. The apparatus should have exactly the dimensions given in the figure, and the temperature of the cooling water should be such that the distillate enters the flask at about 20° C. The flask is heated by a small flame till the fatty acids are just melted, and the flame then turned up to such a height that 110 c.c. of distillate are collected in from 19 to 21 minutes, when ‘ ' i ! N 4 ' ! zs Fig. 44.—Polenske Apparatus. the flame is immediately removed, and the flask replaced by a cylinder. The flask is placed for ten minutes in water at 10° C., and after the physical condition of the insoluble fatty acids has been noted, the contents are well mixed, filtered, and 100 c.c. are titrated as in the Reichert-Wollny process. The whole of the distillate is passed through the filter, and POLENSKE METHOD. 321 the condenser is washed out with 18 c.c. of water, this being collected in the cylinder, poured into the flask, and used to wash the filter; the last 10 c.c. of filtrate should be neut- ralised by one drop of Bs alkali solution. The funnel is removed to the flask in which the distillate was collected, and three suc- cessive portions of neutral v0 per cent. alcohol Rreery (methylated — spirit — will #4 serve) are poured through the condenser, cylinder, and filter, .and the com- bined alcoholic filtrates titrated with FA baryta solution; the number of cubic centimetres used gives the Polenske figure. This method has been investigated by many observers, and it is found that the specification of the method is not quite sufficient to allow of absolutely concordant re- sults being obtained. The author’s investigations lead him to conclude that a very important factor, the temperature of the air around the flask, and the rate of conduction through the walls of the flask and bulb tube is left to chance, and he, therefore, proposes to support the flask on a piece of asbestos cardboard in which a hole 5 cm. in chameter is cut, and to surround the flask with a =—= vessel in which water is Fig. 45.—Steam Jacket. boiled (see Fig. 45). Using this apparatus, it is found that with butters the length of time of distillation can be varied to a considerable extent without affecting the results, but with coco-nut oil the time given should be adhered to. Ltd oH 322 BUTTER. Blank experiments should be performed; the figure for the soluble blank may be sometimes high (2 c.c.), without affecting the accuracy of the results. The soluble acids obtained by the Polenske process are prac- tically the same as those given by the Reichert-Wollny method. The average figure for the soluble fatty acids is 28°4 c.c., but considerable variation is observed; in very rare cases figures slightly exceeding 40 have been obtained, while exceptional low figures of 14 have been observed as lower limits. These very high or very low figures are rare; low figures have usually been observed in cases where the butter is produced from the milk of cows near the end of lactation, especially if the animals have been exposed to inclement weather. The average of the results of different observers shows that out of 100 samples 3 will probably yield Reichert-Wollny figures over 30 c.c. 86 3 29 » between 26 and 30 c.c. 7 2 5 4s es » 25 and 26 c.c. 3 » > rc 5, below 25 c.c. All samples giving below 25 ¢.c. may be looked upon as sus- picious, and should be further investigated. The Polenske figure varies with the Reichert-Wollny figure, and the following table shows the relation :— Reichert-Wollny Figure. Polenske Figure. Mean, Maximum. 32 3:2 3-7 31 3-0 oh 30 2-8 3:3 29 2-7 oo 28 26 atl 27 2-4 2-9 26 ve 28 25 2-1 2-0 24 | 2-0 2-5 ; 23 14 2-4 | 22) \ 8 a5 i 2) 1-7 2-2 | Coco-nut oil gives a Reichert-Wollny figure of 7 to 9 cc., and a Polenske value of 16 to 18°5. Should the Polenske figure exceed the maximum given in the table the quantity of coco-nut oil present may be deduced from P— Pp the formula C = “444 * 100. C = percentage of coco-nut oil. P = Polenske figure. P’ = mean Polenske figure from the table for a figure equa to the Reichert-Wollny figure found + half the Polenske figure. KIRSCHNER PROCESS. 323 Kirschner’s Modification.—To the 100 c.c. of the distillate of volatile fatty acids obtained in the Polenske process, which has been neutralised, 0-5 gramme of finely powdered silver sulphate is added, and after standing for an hour with occasional shaking, the liquid is filtered. 100 c.c. of the filtrate is placed in the dis- tilling flask, 35 c.c. of water, which has been well boiled, and 10 c.c. of the sulphuric acid solution previously used added; a long piece of aluminium wire is placed in the flask, and 110 c.c. distilled as in the Polenske method; of the distillate 100 c.c. are titrated with =I alkali, and after correction for the figure obtained in a blank experiment, the Kirschner figure is calculated by 100 + « ~ 100" (where ys: == the number of ¢.c. of alkali added to the first distillate for neutralisation). The presence of coco-nut oil may be inferred if the Volenske figure is more than 1-0 ¢.c. higher than those given in the table below, multiplying the number of ¢.c. of * alkali by 1-21 and by Kirschner figure, Polenshe figure. 26, « Ore A. pu) oe) ¥ | ah, 1-6 The Kirschner method is of especial value in estimating the quantity of butter in mixtures containing small amounts when large quantities of other fats are present—e.g., in margarine, which under the Margarine Act is not permitted to contain more than 10 per cent. of butter. The percentage of butter may be calculated from the formula K — (0262 PY + 4 09) = Qr242 where B = percentage of butter fat, Kk = Kirschner figure, P = Polenske figure. The following table will give the values of (0-262 P°S + 0-09) :— B P: Value. Pe Value. 0-5, ‘ . 0-26 x, L068 1, : 0-35 Y, 1-13 2, 0-50 10, 1-21 3, 0-61 LI, 1-28 4, 0-72 i 1-34 5, 0-81 13,. . 1-41 6, 0-90 If. 1-47 7, 0-98 15, 1-53 324 BUTTER. A more simple formula, which gives nearly as good results, is pK (O1P + 024) = 0-244 Paal and Amberger distil the fatty acids from 2°5 grammes of butter in steam in a special apparatus, collect 200 c.c. of dis- tillate in from 35 to 40 minutes, wash out the condenser by distillmg 50 c.c. of neutral alcohol. The combined distillates are neutralised, and evaporated, made up to 50 c.c., and 2 to 4 c.c. of a 20 per cent. cadmium sulphate solution are added. The precipitate is collected on a Gooch crucible, washed with not more than 50 c.c. of water, dried, and weighed. The weight, calculated as milligrammes, gives the cadmium figure. The figure for butter usually lies between 70 and 90, and for coco- nut oil 441 to 470; higher results (100 or above) were obtained from the fat of milk yielded by cows fed on large quantities of coco-nut cake or beetroot leaves. Estimation of Saponification Equivalent, or alkali neces- sary for complete saponification. Keettstorfer’s Method.—Keettstorfer proposed to utilise the fact that butter required a greater amount of alkali for its com- plete saponification than most other fats. The method is performed as follows :—A standard alcoholic solution of sodium hydroxide is prepared by dissolving 25 ¢.c. of the 50 per cent. solution of caustic soda recommended by Wollny (p. 317) in 1 litre of strong alcohol; after a day’s repose, during which a little salt settles out, the solution is clear and fit for use. This solution, which should be approximately semi-normal, is standardised against semi-normal hydrochloric acid. About 2 grammes of the fat are weighed out into a small flask, 25 c.c. of the alcoholic soda solution run in from a pipette, the flask connected with an inverted condenser, and the contents gently boiled for fifteen minutes. During the boiling the alcoholic soda solution is standardised; 25 c.c. of the solution are measured from the same pipette, which is allowed to drain for the same length of time as before, and titrated with semi-normal hydro- chloric acid—a little phenolphthalein being added as indicator. The number of cubic centimetres of hydrochloric acid solution should be noted. It is advisable to perform this operation in duplicate. The flask containing the saponified fat is discon- nected from the condenser, a few drops of phenolphthalein solution added, and the liquid titrated with semi-normal hydro- chloric acid till the pink colour just disappears. The number of cubic centimetres used, subtracted from the number required by the 25 c.c. of soda solution alone, will give the equivalent of the SAPONIFICATION EQUIVALENT. 325 alkali required for saponification ; this, multiplied by 0°02805, will give the weight as alkali calculated as potassium hydroxide, KOH; and the figure thus obtained multiplied by 1,000 and divided by the weight of fat taken will express the “ potash absorption ” as milligrammes of KOH per gramme of fat. It is also advisable to calculate the ‘‘ saponification equivalent” (a term due to Allen), which is really an expression of the mean molecular weight. This is calculated from the number of cubic centimetres of normal acid, the definition of a normal solution being that it contains, or is equivalent to, in 1 litre a weight in grammes equal to the equivalent of a substance. It is, there- fore, necessary to calculate the weight of fat which would be saponified by alkali equal to 1 litre of normal hydrochloric acid. Let W = the weight of fat taken. And V =the number of cubic centimetres of semi-normal _ hydrochloric acid equivalent to the alkali required for saponifi - cation. Then the saponification equivalent is expressed by 2,000 W oo The relation between * potash absorption ~ (KK) and * sapont- fication equivalent ”’ (S) is expressed by the formula 56,100 kK Instead of a pipette, the alvoholic alkali may be measured from a burette or automatic measuring apparatus, and the saponification may be conducted in a closed task. An open flask or basin should not be used, as ethyl butyrate, an inter- mediate product of saponification (p. 43), is volatile; this would cause a low value to be obtained. According to Keettstorfer, the potash absorption varies from 221°5 to 233°0 in genuine butters, with an average of 227-0, His experience has been contirmed by numerous observers, and the limits have been extended 218 to 235, The saponiti- cation equivalent varies from 253°3 to 240°8. the averaye being 2471. Other oils and fats have a potash absorption of 190 to 199. with an average of about 195; or a saponification equivalent of 295°3 to 282-0, with a mean of 287°6. Coco-nut and palm-nut oils yield, however, figures which are very different, 246°2 to 268°4. Estimation of the Baryta Value—Avé-Lallemant’s Method. —Two yrammes of butter-fat are saponitied as in the Koettstorfer process, and the solution after neutralisation is evaporated to dryness, 10 c.c. of water is added, and the evaporation con- tinued to remove the last traces of alcohol. The residue is ‘ S= 326 BUTTER. dissolved in boiling water, and the solution, which should measure about 180 c.c., poured into a 250 c.c. flask. The flask is placed be New : : on a boiling water bath, and 50 c.c. of 5 barium chloride solution are added, with constant shaking. After standing on the water- bath for fifteen minutes, the solution is cooled, and made up to 250 c.c. The solution is filtered, the first portions being poured back on to the filter till the solution runs through clear ; the barium is estimated as sulphate in 200 c.c. of the clear filtrate. The streneth of the barium chloride solution is estimated as sulphate in 10 c.c., and 25 c.c. of the alcoholic soda should be neutralised with hydrochloric acid, evaporated, and the residue taken up with water. and a little barium chloride added; any precipitate of barium sulphate due to impurities should be deducted from the amount of barium sulphate obtained from the 50 ¢.c. of barium chloride added. The barium oxide found in 200 c.c. of the filtrate multiphed by 1:25 is deducted from the barium oxide added in 50 c.c. of solution (corrected, if necessary, for the blank), and the value calculated ag milligrammes for 1 gramme of fat. This gives the barium oxide combined with the insoluble fatty acids. The potash absorption is calculated as milligrammes of barium oxide per gramme of fat by multiplying by 1°368, giving the total barium oxide, and the difference between the two values gives the barium oxide combined with the soluble fatty acids. To the last value 200 is added, and the value thus obtained is subtracted from the insoluble value. With butters the difference is always negative, varying from — 23°8 to —0'7, and averaging — 9°6. Other fats and oils give positive values; coco-nut oil giving a difference of 38°9 to 45°1, other oils and fats from 46°9 to 50°3. The soluble baryta value usually varies between 50 and 65 for butters, 54°1 to 57°6 for coco-nut oil, and is very small for other fats. Fritzsche speaks well of this method, and shows that even butters low in Reichert-Wollny figures vive normal results with the Avé-Lallemant process. and Bolton and Revis also strongly recommend it. Estimation of Soluble and Insoluble Fatty Acids— Hehner and Angell Method.—The following method has been adopted by the American Association of Official Agricul- tural Chemists :— Reagents required.—Deci-normal sodium hydroxide. Alcoholic potash. Dissolve 40 grammes of good caustic potash, free from carbonates, in 1 litre of 95 per cent. redistilled alcohol. The solution must be clear. Semi-normal hydrochloric acid accurately standardised. SOLUBLE AND INSOLUBLE FATTY ACIDS, 327 Indicator.—One gramme of phenolphthalein in 100 c.c. of alcohol. About 5 grammes of the sample are weighed into a saponifi- cation flask (250 to 300 c.c. capacity of hard, well annealed: glass, capable of resisting the tension of alcohol vapour at 100° C.), 50 ¢.c. of the alcoholic potash solution added, and the flask stoppered and placed in the steam-bath until the fat is completely saponified. The operation may be facilitated by occasional agitation. The alcoholic solution is always measured with the same pipette, and uniformity further secured by allowing it to drain the same length of time (thirty seconds). Two or three blank experiments are conducted at the same time. In from five to thirty minutes, according to the nature of the fat, the liquid will appear perfectly homogeneous. Saponification being then complete, the flask is removed and cooled. When sufh- ciently cool, the stopper is removed and the contents of the flask rinsed with a little 95 per cent. alcohol into an Erlenmeyer flask of about 200 ¢.¢. capacity, which is placed on the steam bath, together with the blanks, until the alcohol is evaporated. Titrate the blanks with semi-normal hydrochloric acid. Then run into each of the flasks containing the fatty acids 1 ¢.c. more of the hydrochloric acid than is required to neutralise the alkali in the blanks. The flask is then connected with a condensing tube, 3 fect long, made of small glass tubiny, and heated on the steam-bath until the separated fatty acids form a clear stratum. The flask and contents are then cooled in ice-water. The fatty acids having quite solidified, the liquid contents of the flask are poured through a dry filter into a litre flask. care being taken not to break the cake. Between 200 and 300 ¢.c. of water are next brought into the flask, the cork with its condenser tube re-inserted. and the flask heated on the steam-bath until the cake of fatty acids is thoroughly melted. During the melting of the cake of fatty acids, the flask should occasionally be agitated with a revolving motion, but so that its contents are not made to touch the cork. When the fatty acids have again separated into an oily layer. the flask and its contents are cooled in ice-water and the liquid filtered through the same filter into the same litre flask. This treatment with hot water, followed by cooling and filtration of the wash water, is repeated three times, the washings being added to the first filtrate. The mixed washings and filtrates are next made up to 1 litre. aliquot parts titrated with the deci- normal sodium hydroxide, and the total acidity calculated. The number so obtained represents the volume of deci-normal sodium hydroxide neutralised by the soluble acids of the butter fat taken, plus that corresponding to the excess of the standard acid 328 BUTTER. used—viz., 1 c.c. The number is, therefore, to be diminished by 5, corresponding to the excess of 1 c.c. of semi-normal acid. This corrected volume, multiplied by 0:0088 gives the weight of (fatty acids calculated as) butyric acid in the amount of butter fat saponified. The flask containing the cake of insoluble acids and the paper through which the soluble acids were filtered are allowed to drain and dry for twelve hours, when the cake, together with as much of the acids as can be removed from the filter paper, is transferred to a weighed glass dish.. The funnel and filter are then set in an Erlenmeyer flask and the filter washed thoroughly with absolute alcohol. The flask is rinsed with the washings from the filter paper, then with pure alcohol, and these trans- ferred to the glass dish, which is placed in the steam-bath. After the alcohol has evaporated, the residue is dried for two hours mm an air-bath at 100° C., cooled in a desiccator, and weighed. It is heated in the air-bath for two hours more, cooled and weighed. If the two weighings are decidedly different, a further heating for two hours must be made. The residue is the total insoluble acids of the sample. This method has been submitted to numerous modifications ; Hager proposes to add a known weight of wax, picks out the lump, dries, and weighs it. Fleischmann and Vieth advise that the wash- ing should be continued till at-each succeeding washing the colora- tion produced by the addition of a few drops of litmus solution to a few cubic centimetres of the filtrate is not changed. Cassal has devised an ingenious flask, which has a tap at the bottom so that the liquid can be run off, leaving the fatty acids in the flask ; washing can be thus much expedited, as hot water can be added, the fatty acids shaken up with the water, and the water run off, The variation of insoluble fatty acids is from 85°5 per cent. (Bell and Menozzt) to 90°0 per cent. (Reichardt, Cornwall, and others) in genuine butters; the soluble fatty acids calculated as butyric vary from 7°0 per cent. to 4°0 per cent. Most other fats give about 95°5 per cent. of insoluble fatty acids and traces only of soluble fatty acids. Coco-nut and palm-nut oils are, how- ever, exceptions to this, yielding from 82 to 85 per cent. Estimation of the Mean Combining Weight of the Insoluble Fatty Acids.—The fatty acids are dissolved in alcohol, a little phenolphthalein added, and titrated with alcoholic alkali; when a pink colour is obtained a small excess is added (2 or 3 c.c.), the solution heated to boiling for ten minutes, and the excess titrated back, as in the Keettstorfer process. The mean combining weight of the fatty acids is calculated as the saponification equivalent. Direct titration of the fatty acids PHYTOSTERYL ACETATE TEST. 3829 does not yield correct results, owing to the formation of anhy- drides on drying. From the difference between the potash absorption, and the potash used for the insoluble fatty acids, an estimation of the soluble fatty acids can be obtained. Bomer’s Phytosteryl Acetate Method for Detection of Vegetable Oils.——While butter-fat and other animal fats contain cholesterol, vegetable oils are free from this alcohol, and contain phytosteryl. There is a difference in crystalline form and other properties between these alcohols, but the most striking and reliable difference is the melting point of the acetates. Fifty grammes of butter fat are saponified with 100 c.c. of alcoholic caustic potash (200 grammes per litre), 200 c¢.c. of water are added, and the solution shaken out three times with ether, 500 o.c. being used for the first extraction, and 250 c.c. for the others. A larger amount of butter fat may be taken, and shaken out three times with an equal volume of warm alcohol, the alcohol evaporated, and the residue saponified with 20 c.. of caustic potash, the solution diluted with 50 c.c. of water, and shaken out three times with 100 ¢.c. of ether; sufficient of the unsaponifiable alcohol is thus extracted for the test, and the manipulation is easier. The ether is evaporated, and the residue again saponified with a little alcoholic potash solution, diluted with twice the volume of water, and shaken out with three or four successive quantities of ether, The ethereal solution is washed three times with 5 ¢.e. of water, filtered, and the ether evaporated. The residue is transferred to a small basin (this may be accom- plished by not quite distilling off the ether, and pouring the ethereal solution left into the basin), the solvent completely evaporated, and the residue treated with 2 or 3 c.c. of acetic anhydride, and covered with a watch-glass. The acetic anhy- dride is boiled for about a quarter of a minute, and the excess evaporated on the water-bath. The acetate ts dissolved in sutticient alcohol to prevent im- mediate crystallisation on cooling, and the solution left to crystal- lise; when about two-thirds of the aleohol has evaporated, the crystals are separated by filtration, washed with a very little 45 per cent. alcohol, redissolved in hot alcohol, and recrystallised ; the reerystallisation is repeated tive to seven times, and the melting point of the crystals determined after the third and subsequent recrystallisations. Cholesterv] acetate melts at 115-4° C. (corrected). and phyto- sterv] acetate at 127°, if on continued recrystallisation the melting point rises above 117° the presence of phytostery] acetate is ecrtam. 330 BUTTER. Small quantities of paraffin wax are occasionally added, and this interferes somewhat with the test: if this is the case the alcohol should be crystallised from petroleum ether. Although this method only detects vegetable oils, these are so largely used in the manufacture of margarine that this is a very reliable test. Specific Colour Tests for Adulterants. Baudouin’s Test for Sesame Oil.—This test consisted, originally, in shaking the melted fat with a solution of cane sugar in hydrochloric acid. Villavecchia and de Fabris have modified this by using a solution of 2 grammes of furfuraldehyde in 100 c.c. of alcohol to replace the sugar; 10 c.c. of the melted fat are shaken thoroughly with 10 ¢.c. of hydrochloric acid and Ol c.c. of the reagent; a red coloration indicates the presence of sesamé oil. This reaction is very delicate, but is not entirely conclusive. Certain colouring matters—e.q., turmeric and certain aromatic dyes—give a red coloration with hydrochloric acid alone, and, in the presence of these, sesamé oil cannot be detected, as the colour due to sesamé oil would be masked by that yielded by the dye. Furfuraldehyde and hydrochloric acid alone, after some time, yield a reddish colour; hence a slight pimkish tine gradually appearing must not be taken to indicate sesamé oil. Spampani and Daddi have shown that the milk of goats fed with sesamé oil yields butter which gives this test. Hehner, Faber, and others were, however, unable to obtain it with butter prepared from the milk of cows fed on sesamé cake. Sprink, Meyer, and Wagner modify this test, and extract 100 e.c. of butter fat twice with 20 to 30 c.c. of glacial acetic acid at 60° C., evaporate the acid. and test the residue by Bau- douin’s test. To remove the colouring matters which give a red colour with hydrochloric acid they add 10 c.c. of alcohol and 5 c.c. of saturated baryta water to the residue, and evaporate. The residue is extracted several times with petroleum ether,which is evaporated, and the test performed on the residue. They claim that 0°1 per cent. of sesamé oil can thus be detected. Becchi’s Test for Cottonseed Oil.—This test was originally performed by heating the fat with a solution containing silver nitrate, alcohol, ether, nitric acid, amyl alcohol, and rape oil. The reagent has been frequently modified. Bevan prepares the reagent by boiling silver nitrate with amyl alcohol, and cooling the solution. Equal parts of this solution and of the fat are heated in a test tube on a boiling water-bath for ten minutes ; a brown or black coloration indicates cottonseed oil. This test COLOUR TESTS. 33L is by no means conclusive of the presence of added cottonseed oil, as the milk of cows fed on large proportions of cotton cake yields butter which will give a brown coloration. Halphen’s Test for Cottonseed Oil.—One to 3 c.c. of fat are mixed with equal volumes of amyl alcohol, and carbon disulphide containing 1 per cent. of sulphur, and heated in a boiling brine bath for ten to fifteen minutes. A red or orange colour shows the presence of cottonseed oil. If no reaction is obtained a little more carbon disulphide should be added and the heating repeated. Wellmann’s Test for Vegetable Oils.—The reagent con- sists of a solution of sodium phospho-molybdate. It may he prepared by saturating 5 grammes of molybdic acid with sodium carbonate solution, adding 1 gramme of sodium phosphate, evaporating to dryness and fusing. The mass is dissolved in boiling water, and concentrated nitric acid (5 to 7 ¢.c.) is added till the yellow shade is permanent. The solution is then made up to 100 ¢.c. One gramme of fat is dissolved in 5 ¢.c. of chloroform and shaken with 2 c.c. of the reavent for one minute. A ereen color- ation (changing to blue on addition of ammonia) is formed in the aqueous layer when vegetable oils are present. Coco-nut oil is not, however, detected by this means, Behaviour of Butter Fat with Solvents. Critical Temperature of Solution.—Crismer recommends that several drops of the melted and filtered fat be introduced: into a small tube 10 millimetres in diameter and 100 to 120 milli- metres long by means of a capillary pipette. An equal volume of alcohol is added and the tube sealed and fastened by a platinum wire to the bulb of a thermometer ; it is then heated in a bath of sulphuric acid till the meniscus separating the two layers becomes a horizontal plane. At this point the thermometer . is withdrawn from the bath, and turned sharply two or three times until the liquid becomes homogeneous. after which it is replaced and the temperature allowed to fall slowly. the ther- mometer and tube being constantly shaken. The temperature at which a marked turbidity is produced in the hquid is the critical temperature of dissolution. If absolute alcohol be employed an open tube may be used. The alcohol used should have a specific gravity of O7967 at 153° C.. if the specific gravity differs 0°106° should be added or deducted for cach 00001 below or above 07967. When examining butter fat it is necessary to estimate also 332 BUTTER. the acidity by titrating 2 c.c. with x alkali and adding the figure thus obtained to the critical temperature. Crismer has shown that the critical temperature varies with the percentage of insoluble fatty acids. Table LXXVIII. will show the variations. TABLE LXXVIII. Critical Temperature. | Critical Temperature. Alcohol 0°8195 sp. gr. | Absolute Alcohol. ctusuluble Fatty Acids. I | Below 100° | Below 54° i 86 to 88 100% to 108° B4° to 622 | 88, 905 108° ,, 118° | 62”, 727s, 93-3 lis’ ,, 124° | 722, 78° OBC, 95-5 Butter usually has a critical temperature of 53° to 57°, and in exceptional cases 59°. The Reichert-Wollny figure may be calculated by the formula R-W = 129° — critical temperature (with alcohol of sp. gr. 0-8195). =&35- ., 5 (., absolute alcohol). Valenta’s Method—Solubility in Acetic Acid.—Valenta showed that there was an enormous difference in the tempera- tures at which various fats and oils dissolved without turbidity in acetic acid. By the work of Allen and Hurst it was shown that the strength of acid made a considerable difference. Chatta- way, Pearmain, and Moor have investigated the subject and recommend the following procedure for butters :—2'75 grammes of butter fat which has been previously dried (preferably by mixing with dried pellets of filter paper and filtermg through a dried filter) are weighed into a test tube provided with a stopper ; 3 c.c. accurately measured of acetic acid (containing 99°5 per cent. CyH,O.) are run into a tube, and this is placed in a beaker of water. The water is gradually heated and the tube shaken till the solution is clear ; the water is then allowed to cool gradu- ally, and the temperature at which a turbidity appears in the tube is measured by a thermometer held in close proximity. By shghtly warming up and cooling down again, a second deter- mination can be obtained. Undue heating of the sample should be avoided, both in the preparation of the fat for analysis and during the performance of the test. IODINE ABSORPTION. 333 They give figtres as follows :— Maximum. Minimuni. Average. Butter fat, - 39:0° C. 29-0° C. 36-0° C. Margarine, . . 97-0°C, 940° C. 95-0° C. KE. W. T. Jones prefers, instead of using an acid of estimated strength, to test it against a standard sample of butter, and to dilute the acid so that it gives a temperature of turbidity of 60°. Margarine then gives about 100°. Hehner has found that this test depends almost entirely on the glycerides of the saturated fatty acids present, as these are almost completely deposited on allowing the acetic acid to cool. The Iodine and Bromine Absorption. Von Hiibl’s Method; Wijs’ Modification. —This method depends on the fact that acids of the oleic, linolic, and linolenic series contain unsaturated bonds, and, under suitable conditions, combine with iodine and bromine. For the iodine absorption, it has been shown that the presence of iodine chloride is necessary. The process 1s worked as follows :— Reagents.—13 grammes of iodine wre dissolved in pure 99 per cent. acetic acid, and chlorine passed in till the strenuth of the solution is doubled: this point is sharply shown hy a change of colour. Deci-normal sodium thiosulphate solution. Dissolve 25 grammes of pure sodium thiosulphate solution and 1 yramme of salicyhe acid in 1 litre of water. Allow this to stand a few days and filter. This solution is permanent and does not alter in strength. To standardise the solution, about 0°25 vramme of resublimed iodine is accurately weighed in a small stoppered flask, about 2 grammes of potassium jodide and 2 ¢.c. of water are added, and the flask yvently shaken till the iodine is dissolved. The iodine solution is diluted with water. transferred to a larger flask, and titrated with the sodium thiosulphate solution till the yellow colour just disappears. This operation is repeated two or three times. The mean strength of the iodine deduced from these experiments is noted on the label of the bottle. A 10 per cent. (approximate) solution of potassium iodide and a starch paste solution, made by pouring an emulsion of 1 gramme of starch in a Jittle cold water into 200 ¢.c. of boiling water, and boiling for ten minutes: if a little mercuric iodide be added. this solution is permanent. The process is performed as follows :—About 0°5 gramme of the fat is accurately weighed in a glass stoppered flask holding at least 100 c.c.: 10 ¢.c. of carbon tetrachloride are added, and 334 BUTTER. the flask gently rotated till the fat is dissolved; 20 c.c. of the iodine chloride solution is next added and the whole well mixed. The flask is now put aside for half an hour. At the same time one or more blanks—.e., flasks contaming 10 c.c. of carbon tetrachloride and 20 c.c. of iodine chloride solution should be put aside with the tests. After half an hour, 10 c.c. of potassium iodide solution are added to each flask, and the contents are washed out into a larger stoppered bottle with distilled water. The standard thio- sulphate solution is run in with continued shaking till only a faint yellow colour remains; a little starch paste is added, and the thiosulphate solution run in, drop by drop, till the ‘blue colour disappears. The quantity of thiosulphate solution used for the flask in which the sample was placed subtracted from the mean of the blanks will give the equivalent of the iodine absorbed. This, multiplied by the strength of the solution, will give the weight of iodine. By multiplying this by 100 and dividing by the weight of fat, the percentage of iodine absorbed is obtained. The following examples will make the mode of calculation clear :-— : Experiment 1. Weight of fat taken, 0-5006 gramme. Titrated with 26-48 c.c. of thiosulphate solution. » 2. Weight of fat taken, 0-4991 gramme. Titrated with 26-55 ¢.c. of thiosulphate solution. Blank No. 1 took 43°35 oy 5 55 29 2 29 43+ 45 2? 22 2? Mean, 43-40, 1 c.c. of the thiosulphate solution was equal to 0001187 gramme of iodine. Therefore 0-5006 gramme absorbed (43-40 — 26-48) x 0-001187 gramme of iodine. = 0-2008 gramme or 40-11 per cent. = 0-4991 gramme absorbed (43-40 — 26-55) 0-001187 gramme of iodine. = 0-2000 gramme or 40-07 per cent. Bromine Absorption.—Instead of using the iodine chloride solution, a solution of bromine in chloroform, or, what is far preferable, carbon tetrachloride may be used. Four c.c. of dry bromine (this is best dried by shaking bromine with anhydrous calcium chloride, decanting, and distilling from a small stoppered Wiirtz flask fitted with a good condenser) are dissolved in 1 litre of dry chloroform or carbon tetrachloride. The process is performed as above described, except that there is no need to wait before titrating; this may be performed at once. 20 ¢.c. of the bromine solution are substituted for the 20 c.c. of iodine chloride solution. It is advisable also to increase the amount of potassium iodide solution added to 20 c.c. or more. BROMINE ABSORPTION. 335, Gravimetric Method of Hehner.—Hehner has proved that the bromine absorbed may be estimated gravimetrically. The fat is weighed in a small basin. dissolved in carbon tetrachloride, a solution of bromine in carbon tetrachloride added, and the ‘excess of bromine and the carbon tetrachloride evaporated on a water-bath in a good draught cupboard. The residue is freed from the last traces of bromine by adding several successive portions of carbon tetrachloride and evaporating them, and, finally, by drying in an air-bath maintained at a temperature somewhat above 100° C. The increase in weight multiplied by oe 15875 will give the iodine absorption. Thermometric Method.— Hehner and Mitchell have also devised a most ingenious means of rapidly and accurately cal- culating the iodine absorption, founded on the fact that when 1 molecule of bromine combines with 1 molecule of unsaturated fat a definite amount of heat is liberated. One gramme of fat is weighed into a jacketed test tube about 1 inch in diameter and 6 inches Jong, from the jacket of which the air has been exhausted. 10 c.c. of chloroform are added, and the temperature noted; 1 ¢.c. of bromine is added, the mixture stirred with the thermometer, and the highest point to which the temperature rises is recorded. The difference between the initial and the highest temperatures multiplied by a factor will give the iodine absorption. The factor must be found empirically, as it varies slightly with each apparatus, ther- mometer, etc. It can be easily ascertained by submitting a few fats of known and varying iodine absorption to this test, and taking the mean relation between the difference of temperatures noticed and the iodine absorption. Hehner and Mitchell found in their experiments that the temperatures multiplied by 5:5 gave the iodine absorption. The thermom ter used should be a good one, capable of reading to 75° C., the same thermometer and test tube should always be used. When the apparatus has been once standardised this method forms a rapid means of estimating the iodine absorption. The bromine should be measured in a 1 c.c. pipette, having a bulb filled with soda lime in its upper portion; unless this is done, the fumes of the bromine are apt to prove very unpleasant. The bromine thermal test for oils and fats is modified by Gill and Hatch by taking sublimed camphor as the standard substance, and dividing the rise with the fat by that with the camphor to a “ specific temperature reaction.” They tind that this multiplied by 17°18 gives a figure very close to the iodine absorption. 336 BUTTER. Heat Evolved by Hydrolysis by Sulphuric Acid. The Maumené Test.—When fats are acted on by strong sulphuric acid a series of reactions takes place. The fat is first split up to fatty acids and glycerol, which combines with the sulphuric acid. The saturated fatty acids (stearic series) are not further affected, but the unsaturated fatty acids undergo sul- phonation and other changes. Of these, the oleic series, which has only one saturated bond, is acted on to a less degree than the linolic and linolenic series, which contain two or three bonds respectively. Hach of the actions which takes place evolves heat, and, by measuring the rise of temperatures which takes place, an index of the total amount of heat evolved is obtained. Modification by Thompson and Ballantyne.—This test 1s due to Maumené, who measured the heat evolved on mixing 10 ¢.c. of sulphuric acid with 50 grammes of an oil or fat. His original method was faulty, in that he did not rigidly prescribe any strength of acid nor form of apparatus. Thompson and Ballantyne propose to compare the heat evolved on mixing 10 c.c. of sulphuric acid with 50 grammes of oil or fat with that evolved by mixing 10 ¢.c. of the same acid with 50 grammes of water in the same vessel. Taking the heat evolved by the water as 100, they term the figure obtained the ‘Specific Temperature Reaction’ of the oil or fat. This method gives a very fair means of correcting for the differences of temperature observed when working with acids of differing strength and in different apparatus, and is convenient in practice. The author has examined with some care the results obtained by the use of acids of different strengths. The following series will show that the effect of strength of acid can be corrected by a very simple calculation. These results were obtained with a pute olive oil. TABLE LXXIX. | Strength of Acid. Rise of Temperature. er ee 1m 100-00 per cent. HeSO,4, . 47°2° 47°2° 97) 35 Re : 411° 466° 96°64 o is ‘ 39°3° 46 '6° 94-93 7 sis - 356" 46°6° 93°49 Pe " i 326° 46 8° 92-85 7 56 7 34 46 9° 92°04 0 a e 29°0° 46°3° a Mean, 46-7° MAUMENF. FIGURE. 337 The results calculated for 100 per cent. acid were obtained by the following formula :— 21:5 per cent. H,SO, — 78-5 = rise of temp. with 100 Rise of temp. x per cent. acid. _ Richmond Modification.—The author calculates the “ Rela- tive Molecular Maumené ”’ figure by the following formula :— (215 20th 195 2-785" 39“ 3 where R=observed rise of temperature. a=percentage of H,SO, in acid. h=heat capacity of apparatus. K= potash absorption (per cent. ). R.M.M.=R x 25 grammes of oil were used and 5 c.c. of acid. The method is performed as follows :—A beaker about 1} inches in diameter and 3 inches deep is fitted, by means of a ring of cork, inside a slightly larger beaker; this is placed in a third still larger beaker, and the intermediate space packed with cotton wool. The heat capacity of this apparatus is next deter- mined; about 10 grammes of water are placed in the innermost beaker and the temperature noted ; about 25 yrammes of water of higher temperature are added, and the final temperature noted. The heat equivalent of the apparatus is calculated by the formula— pas) —23 e-a where h=heat capacity of apparatus. x=weight of water placed in beaker. y= weight of hot water added. a=temperature of apparatus. b=temnerature of hot water. c=final temperature after mixing. The following experiments will show the nature of the value of h:— he a, y. b. G. h. KrYaummes, grammes. grammes, 10-0 16-0° 26°5 39-0° 31-2° 3-60 10-0 17:5° 23-5 50-3° 38-5° 3-43 0-0 20-0° 35:1 42-0° 40-0° 3-51 When the innermost beaker holds about double the volume of the oil and acid, its weight multiplied by 0°15 will give its heat capacity with considerable accuracy; the beaker used above weighed 232 grammes ; this multiplied by 0°15 gives 3-48. Twenty-five grammes of filtered and dried fat are weighed into the beaker, and the apparatus with thermometer, together = 338 BUTTER. with the acid to be used in a small bottle, and a 5 c.c. pipette, are placed in an incubator kept at 30° C. for at least half an hour, and the temperature noted. 5 ¢.c. of acid are added, and the mixture well stirred with the thermometer, till the tempera- ture ceases to rise. The difference between the initial tempera- ture and that finally attained is taken as the rise of temperature, and the Relative Molecular Maumené figure is calculated from this. The R.M.M. of butters varies from 33°0° to 34°5°, with a mean. value of 34°0°. The ratio EM 0 has been about 0°633, iodine absorbed varying from 0°615 to 0°649. Any increase in this ratio may be taken to indicate adulteration by vegetable oils. This method is occasionally useful, but is rather troublesome, and cannot be well recommended, except as an additional test in cases of doubt. It is very important that the fat be well dried. The Physical Examination of Butter Fat.—The most important physical properties are microscopic examination under polarised. light, density, refractive index, viscosity, and behaviour on melting. Microscopic Examination under Polarised Light.— This. method is founded on the fact that when a crystalline substance is placed between two crossed Nicol prisms the light undergoes rotatory polarisation; the rays that would normally vibrate in the plane, which would cause total reflection, are caused to vibrate in a plane inclined to this, and the light consequently passes through the second Nicol prism. Substances which have no crystalline structure do not cause any interference with the plane of vibrations. This method was first applied by Campbell Brown to detect. adulteration of butter with foreign fat. The fat of milk when churned into butter is devoid of crystalline structure. The fats of which margarine 1s composed, having been melted and cooled, usually acquire a more or less pronounced crystalline form. It has been studied by Taylor, Pizzi, and others, and is fairly reliable. The following are the sources of error :—The presence of salt, salicylic acid, and other crystalline substances added to. butter as preservatives, or accidentally mixed with it, will cause the light to pass, and may be mistaken for crystalline fat; but. a simple microscopical examination will usually reveal the nature of particles of this nature, and an experienced observer will rarely be misled. Butter which has been melted, re-emulsified, and rechurned will behave to this test as margarine, though no similar appearance is noticed in butter which has been kept just below the melting pomt for some length of time. Margarine which has been prepared by emulsifying the fat with skim milk MICROSCOPIC EXAMINATION UNDER POLARISED LIGHT. 339 with a good emulsor, separating the cream, and churning this with ordinary cream, behaves as butter, and Pizzi has succeeded in adding 30 per cent. of foreign fat to butter in this way without being able to distinguish it. Finally, rancid butter, and butter which has been at once churned from pasteurised cream at a low temperature, may sometimes give an appearance resembling margarine. Butter prepared from clotted cream shows many crystalline particles (Fig. 46). It is apparent that this test must be used with reservation, but it is without doubt of use as corroborative evidence in cases where other analytical data are not absolutely conclusive. The method is carried out as follows :—The outer portions of a piece of butter are removed, and a piece about the size of a pin’s head is transferred from the freshly exposed surface to a clean microscope slide. A cover glass is placed on the top, and Fig. 46.—Butter under Polarised Light. the butter spread out by ventle pressure on the upper surface of the cover. The slide is placed on the stage of a microscope fitted with crossed Nicol prisms, and examined with a I-inch objective or higher power. To exclude light from the upper surface a blackened cardboard tube may be placed over the slide in such a manner that the objective dips into it, and the light falling on the upper portion of the slide is cut off. When pure butter is examined the field is uniformly dark, and only with the greatest difficulty can any structure be distinguished. When margarine is present certain portions of the field have a bright appearance, and indistinct crystalline forms can be made out. If any distinct and bright crystals are seen, the Nicol prisms should be turned parallel, and the slide examined in that spot in order to see whether salt or other crystalline matter is present; there is not 340 BUTTER. much difficulty in distinguishing this owing to its great refrac- tive power. The slide should be moved about to examine all parts of it, as, in cases of small amounts of adulteration, the margarine is not equally distributed throughout, and two or more portions from different parts of the sample may be examined. As a check, a selenite plate (a crystalline form of calcium sulphate, which possesses the property of rotatory dispersion to a large extent) is next placed under the slide, the microscope focussed, and the sample again examined. In this case the slide will be uniformly illuminated when the prisms are crossed, but will appear coloured; the colour depends on the thickness of the selenite and the position of the Nicol prisms, but when pure butter is examined the whole of the field appears of one colour. When margarine is under observation certain parts of the field are seen to be of a different colour. Fig. 47.—Margarine under Polarised Light. This modification is, when used by persons of absolutely normal vision, quite as delicate as the examination without selenite, but it cannot be generally recommended, as the per- ception of colour is a sense in which many people—more than is commonly supposed—are somewhat deficient, though not abso- lutely colour blind. The usual colours which selenite plates are constructed to give—red and green—are those which are least easily distinguished by the majority of those who suffer from weak colour perception. It is advisable, therefore, never to omit the examination without a selenite plate. It is, of course, essential to employ a good microscope, as any illumination of the slide, except by light which has passed through the polariser, will prevent the extinction of the field on crossing the Nicol prisms. Though it is impossible in practice MICROSCOPIC EXAMINATION. 341 to secure an absolutely dark field, this can be done with a good instrument and a cardboard tube over the slide with a near approach to completeness. Any marked illumination of the field when the Nicol prisms are crossed will greatly impair the delicacy of the test. Microscopic Examination after Treatment with Sol- vents.—A. Zega has suggested the following process :—The sample is melted and filtered into a test tube, which is kept for two minutes in a boiling water-bath. By means of a hot pipette 1 c.c. is measured into a 50 ¢.c. stoppered tube containing 20 c.c. of a mixture of 6 parts of ether, 4 of alcohol, and 1 of glacial acetic acid. The whole is well shaken, and allowed to cool in water at 15° or 18°C. Pure butter remains clear, and only gives a slight deposit after standing one or one and a half hours. Mar- garine shows a deposit in one or two minutes, and in ten minutes yields a copious precipitate. Mixtures of butter with 10 per cent. of margarine begin to separate in about fifteen minutes. As soon as a few solid particles have fallen, they are withdrawn and examined under the microscope. Genuine butter appears in long, very narrow crystalline rods, often pointed at the ends, sometimes bent, and usually joined together centrally into more or less symmetrical open stars. Margarine crystals consist of bundles of minute needles packed closely together into circles, sheaves, or dumb-bell-like masses. Mercier digests 1 c.c. of melted fat with 30 c.c. of 90 per cent. alcohol for five minutes at 50° to 55° C., the fat and alcohol being well mixed ; and after fifteen to twenty minutes’ standing 20 ¢.c. of the alcoholic solution are withdrawn, cooled to 30° to 40° C., and filtered ; the fat is then slowly allowed to crystal- lise, and the crystals filtered out and examined by the micro- scope. If coco-nut oil is present, little round bunches of crystals consisting of long needles are observed. Hinks has also devised a process, which depends on the crystal- lisation of coco-nut oil from alcohol; 5 c.c. of butter fat are dissolved in 10 c.c. of ether in a test tube, which is then packed with ice. After half an hour, the clear ethereal solution is filtered through a pleated filter, the filtrate evaporated, and the residual fat boiled with three or four times its volume of alcohol (96 to 97 per cent. by volume—the strength is important). Complete solution takes place at the boiling point, and the liquid is allowed to cool to room temperature, and then placed in water at 5° C. for fifteen minutes. The alcoholic solution is rapidly filtered into a tube, which is kept at 0° C. for two or three hours. The flocculent deposit is examined by the microscope, using a magni- fication of 250 to 300 diameters, preferably on a cooled stage ; butter deposits glycerides in round granular masses, but coco- 342 BUTTER. nut oil yields fine needle-shaped crystals; a mixture shows the granular butter spores, with numerous fine, almost feathery, crystals generally attached to the butter granules. Five per cent. of coco-nut oil can be detected by this test. The Density of Butter Fat. Butter fat, on account of the presence of glycerides of low molecular weight, has a greater density than the fats used for its adulteration. As it is more convenient and exact to take the density of a liquid than of a solid, the fat is almost invari- ably melted and the density determined at a temperature above its melting point. The methods of estimating the density have already been discussed under the “specific gravity of milk” (p. 60), and (except that for butter a temperature considerably higher than that at which the density of milk is taken is employed) the same methods are employed. Expansion.—Two questions arise: At what temperature shall the density of butter be taken? How shall the results be expressed? The experiments of Skalweit have indicated the most favourable temperature. He took the densities of butter and margarine at various temperatures from 35° C. to 100° C., using Koch’s incubator to keep a constant temperature. His figures are as follow :— TABLE LXXxX. ‘Temperature. Butter. Margarine. Difference. t 35° C 0-9121 0-9017 : 0-0104 BOP 5 0-9017 0-892] 0-0096 60° 0-8948 0-8857 0-0091 70° ,, 0-8879 0-8793 | 0-0086 80° ,, 0-8810 0:8729 : 0-0081 90° ,, 0-8741 0-8665 0-0076 100° ,, 0-8672 0-8601 | 0-0071 | ; Mode of Expressing Results.—These figures clearly show that as the temperature rises the densities of butter and mar- garine tend to approach one another; the widest difference occurs at 35° C.; he, therefore, recommends that this temperature be adopted as the temperature at which the densities of butter should be determined. In England a large number of determinations have been made by J. Bell, Allen, Muter, and others at a temperature of 100° F. DENSITY. 343 (37'8° C.), and this temperature is very near that found by Skal- weit to give the largest difference. In America the temperature of 40° C. is used to a considerable extent, and the author has taken a large number of densities at cee C. (owing to the use of a thermometer which read 0°5° too igh). Estcourt proposed to use the temperature of boiling water {which he found to raise the butter fat to 97°8° C. [208° F.]), as being easily attained. Allen and others have warmly recom- mended this temperature, and find no difficulty in bringing the temperature up to 99° C, There is a certain amount of confusion as to the manner in which densities are expressed. To ascertain the true density, the weight of a certain volume of fat should be divided by the weight of the same volume of water at the same temperature and multiplied by the density of water at that temperature. This is very rarely done, so that few published figures are true densities. Muter gives the term “actual density” to the weight of a certain volume of fat divided by the weight of the same volume of water at the same temperature; densities expressed thus 37°8° 37°8° . are usually denoted by the symbol D for density at 37°x?, or D a for density at 35°, and the true density is often ex- 37°8° 35° pressed as D eo or D ro It is usual when densities are taken at the temperature of boiling water to express them in a different way. The weight of a certain volume of fat is divided by the weight of water displaced by a piece of glass which occupies the same volume at the same temperature, when it is cooled down to 60° F. (15°5° C.). This mode of expression may be denoted by the formula D se in glass. Though apparently cumbersome this method of expressing results has certain advantages, as the instrument with which the densities are taken can be standardised at 60° F. (155° C.), and can then be used at any temperature without requiring to be restandardised. It must be remembered that, though the expansion of glass is very nearly constant, it is not quite so, and over a range of 85° C. appreciable differences may occur in the expansion of different instruments. If the glass be not well annealed, internal strains are set up, and these may be so accentuated at high temperatures as to cause distortion and change of volume. It will be readily seen that the method of taking the apparent density in glass at the temperature of 344 BUTTER. boiling water is liable to greater experimental error than deter- minations at lower temperatures, and, as the experiments of Skalweit have shown, that the effect of experimental error is magnified at 100° C., owing to there being a smaller difference between the densities of butter and margarine at this tempera- ture than at lower ones. It is desirable not to adopt this method where accuracy is, as it always should be, a desideratum. On the whole, it seems desirable to adopt 100° F. (37°8° C.) as the standard temperature at which determinations should be made, because it is sufficiently near Skalweit’s minimum to give a large difference between butter and margarine, and because a large number of experiments on genuine butters have already been made at this temperature. Determination.—The density of butter is best determined by the pycnometer. This is filled with distilled water, and the weight of the water which it holds at 37°8° determined. After drying, by placing in the water oven and drawing a current of air through it, it is filled with the fat and placed in water at 37°8° C. till the volume is constant; the temperature must be accurate to 0'1° C. if the result is required to be exact to the fourth place of decimals. The weight of fat divided by the 37°8° 378°" The Westphal balance may be employed, the apparent density of water at 37°8° must be determined, and the density of fat indicated by the instrument divided by this to obtain the density ' 37°8° ae The density is also sometimes determined by a hydrometer. If this instrument be used, it should be tested in fats of known density, and its indications thus controlled. A. Meyer states that the height of the meniscus depends somewhat on the baro- metric pressure, but the error due to this cause is not likely to exceed the experimental error of reading. Should the tempera- ture not be exactly 37°8° C., a correction of 0°0007 for each degree may be added for temperatures above and subtracted for temperatures below, 37°8° C. weight of water will give the density at If it be desired to take apparent densities at te in glass, the instruments should be standardised at 15°5°, and the density determined as above. The author has used a bulb of specific gravity 0°865 at 15°5° for the purpose of determining rapidly an approximate density. A test tube is filled with the fat, the bulb dropped in, and the tube placed in boiling water. If the bulb floats at the top. the DENSITY. 345 density is above 0°865; and if it sinks, it is below. This has proved a fairly good rough test. The limits observed for pure butter are :— amie Maximum. Minimum. Mean. At 37-8 0-9140 0-9094 0-9118 100°. At Tea? (in glass) 0-8685 0-8650 0-8667 The fats usually employed as adulterants have a density at 37°8° of 0°901 to 0°905, mean 0°903; and at (in glass) of 37°8° 0°860 to 0°863, mean 0°861. : : ; . 00° Certain oils have, however, a higher density; thus, at ae (in glass)— Palm-nut oil has a density of 0-873 Coco-nut oil, 0-874 Cotton-seed oil, 08725 Arachis oil, 0-863 Sesamé oil, 0°8675 Of these oils, palm-nut and coco-nut oils can be readily detected (see Fat), while the other oils cannot be used alone, but must be mixed with fats of less density to obtain the neces- sary consistency. With the reservation that the oils mentioned above would cause somewhat abnormal results, the determination of the density of butter is a very useful test, and, though not reliable as a single test, is of great use for corroborative purposes. Molecular Specific Volumes.—A method of calculating which will sometimes be of use is to deduce the specific volume by dividing the density into 1, and to multiply the figure thus obtained by the potash absorption and to divide the result by 19°5, The mean figure thus obtained for butter is 1°2766, and for margarine 1:1641 at 37°8° C. If the butter is adulterated with beef or other animal fat, the percentage of adulteration calcu- lated with this figure will agree fairly well with that calculated from other determinations. If vegetable oils have been used, the percentage deduced thus is considerably more. Refractive Index. The Oleo-refractometer.—When light passes from one medium to another it only passes in a straight line when it falls perpendicular to the surface separating the two media. If it passes through at an angle to the surface, it is bent or refracted. 346 BUTTER. and the ratio between the angle made by the path of the ray with the perpendicular to the surface in the first medium and the angle made by the path in the second medium with the perpendicular is a constant; the ratio of the sines of the two angles is known as the index of refraction. As the sine of an angle of 90° is 1, it is seen that the ratio between the sine of the angle at which light is first reflected and 1 is the index of refrac- Fig. 48.—Oleo-refractometer. tion; this angle is termed the angle of total reflection. As it is more convenient to measure this than to measure the two angles, and deduce the ratio of the sines, in practice the angle of total reflection is frequently measured. Miiller was the first to apply the determination of the refrac- tive index to the analysis of butter. He allowed the butter to REFRACTIVE INDEX. 347 solidify slowly, absorbed the liquid portion with filter paper, extracted this with ether, and examined it in Abbé’s refracto- meter, an instrument which measures the angle of total reflection. Skalweit examined this method and showed that it was important to operate at a fixed temperature. Owing to the difficulty of maintaining a fixed temperature in Abbé’s refractometer, this method was not much used till special instruments were devised. Amagat and Jean have devised an oleo-refractometer for deter- mining the refractive index of oils and fats (Fig. 48) ; it consists of a collimator, a hollow prism with sides inclined at an angle of 107°, and a telescope furnished with an arbitrary glass scale placed in the focus of the eye-piece. In the collimator is placed a piece of opaque substance, which cuts off the light from one- half of the field. If the prism and the space outside between the collimator and the telescope are filled with the same liquid, there will be no refraction. If, however, the prism contains a different liquid, the refraction will be indicated (in arbitrary degrees) by the position of the junction between the light and dark halves of the field on the scale. A standard oil (hu7le type) * is supplied with the instrument, and the scale is so adjusted as to read zero when this is placed in the instrument. The oil or fat to be tested is placed in the hollow prism and the position of the dividing line read off on the scale. The temperature is kept constant by means of a jacket, and is usually 45° C. Jean gives the following method for testing butter :—Melt from 25 to 30 grammes of the butter in a porcelain dish at a temperature not exceeding 50° C.; stir well with a pinch or two of gypsum, and allow to settle out at about the same tempera- ture. Then decant the supernatant fat through a hot water funnel plugged with cotton wool, and pour (while warm) into the prism. Observe the deviation at 45°. Genuine butter gives a deviation of about 30° to the left, while margarine gives about 15°, and |coco-nut oil about 59° Lobry de Bruyn has shown that genuine butters may show a deviation of 25° to the left. It is evident that the addition of a mixture of coco-nut oil and margarine would give a figure equal to that of butter. Muter has, however, shown that the figure given in the oleo-refracto- meter has a relation to the Reichert figure, which would be much disturbed by such a mixture. Muter’s relation is expressed by Table LANNY. * This is usually translated as “typical oil’; the word “ standard ”’ is more nearly equivalent to the French “type,” than is ‘‘ typical.” 348 BUTTER. TABLE LXXXI. A deviation of - 36° is os by a Reichert figure of 16:0. 45 — 35° 5 Pe 15°25. ~ 34° ‘ : 145. ” ~ 33° ” ” 13°75. $5 ~ 32° +9 a 13 0. o ~ 31° ae aie 12:25. ” - 30° vy ” 11°85. n - 29° ” ” 10°75. Fig. 49.—Butyro-refractometer. measures the angle of total reflection and is a modification of the well-known Abbé refractometer. It consists of two prisms of glass, hinged so that they can be separated. The light enters at the bottom, passes through the prisms, and is viewed through a telescope having a fixed scale in the focus of the eye-piece. The prisms are provided with a jacket, through which water, the temperature of which is indicated by a thermometer, is passed. BUTYRO-REFRACTOMETER. 349 A drop of the filtered fat is placed on the glass surface of the lower prism, spread evenly over it, and the prism closed; the reflector is adjusted so as to reflect clear daylight or lamplight through the prisms, and the refractive index in scale degrees is read off. This instrument is extremely rapid, as a determination, in- cluding reading of the temperature and scale degrees, does not take more than a minute. After use, the instrument should be cleaned by rubbing off the fat with a duster, and polishing the prisms with a clean linen cloth slightly moistened with alcohol. Scale divisions may be converted into refractive indices by Table LXXXII. TABLE LXXXII. i Seale Division. Retiachive Indies for the Difference. 0 1 42e0 Say 10 14300 8-0 20 1°4377 77 30 14452, 75 40 14524 ie 50 14593 6°9 60 1:4659 66 70 1:4723 6-4 80 1:4783 6-0 90 14840 57 100 14895 5:5 There is a difference in the refractive index depending on the light used; this is corrected in the instrument by making the prisms of different kinds of glass, so that when used with butter ordinary white light behaves as if it were simple light. Other fats (and adulterated butters) may be tinged at the edge with blue or red. In this case it is not easy to read the dividing line accurately. The author is in the habit of using the sodium flame, obtained by heating sodium chloride in a Bunsen burner, as the source of light, and finds that absolutely sharp readings can thus always be obtained. The readings with butters do not differ, whether white light or sodium light be used. The refractive index varies 0°55 scale degree for each 1° C., and can be corrected by means of this factor if the temperature differs from that adopted as normal. For the correction of scale readings taken at any temperature to any other temperature or to that adopted as a standard, Leach and Lythgoe have devised a slide rule, but. except for small 350 BUTTER. differences of temperature, the author finds that the readings are not strictly correct. A chart for the correction of butyro-refractometer readings for temperature may be constructed thus :—Select a sheet of squared paper at least 120 units by 200 units wide; at a point 34 units from the bottom, set out horizontally a series of points 5 units apart, and at a point 119 units from the bottom a similar series of points 7 units apart; join the corresponding pairs of points to form a series of temperature lines. The middle vertical line is selected as the standard temperature, say 35°, and each line to the right will represent a temperature 1° higher, and to the left 1° lower than the next preceding line. From the bottom at a point 100 units from the standard temperature line to the left draw a line to the point which lies 20 units from the bottom and 100 units to the right of the standard temperature line; this will represent 0° on the scale of the butyrometer; draw parallel to this a series of lines 10 units apart measured vertically, and mark these 10°, 20°, etc., of the refractometer scale. To use the chart, find the point of inter- section of the lines corresponding to the observed temperature, and scale lines (differences between the lines can be estimated with sufficient accuracy by the eye), and the distance measured horizontally between this point and the vertical standard line will give the correction to be added if on the right, or subtracted if on the left; 10 units of distance equal one scale degree of correction. This chart is easy to make, and still easier to use, and the author has found it to give very accurate results over a con siderable range of temperature, not only for butter, but also for other oils and fats, and for the standard fluid. The author has found that genuine butters vary from 43°7° (in a sample giving a Reichert value of 16°0 ¢.c.) to 49°0° (in a sample giving a Reichert value of 10°5 ¢.c.), and average 46°0° at a temperature of 35° C. The value 47°0° has been proposed as a practical limit. The equivalent at other temperatures of this limit is as follows:— Temperature. Scale Division. | ‘Lemperature. Scale Division. 26° 52-5° 40° 44-2° 30° 49-8° 45° 41-5° 35° 47-0° Some importance has been attached to the colour observed at the edge of the dividing line, and a blue colour has been alleged to be indicative of margarine. In the author’s experience this property is valueless. Thus the sample giving a reading of 43°7° was tinged red, and that giving 49°0° was tinged blue, though both were authenticated as genuine butters. BUTYRO-REFRACTOMETER. 351 Margarine has a value of about 52° at 35°, coco-nut oil of 41°, and cotton-seed oil of 61°. The remarks made upon the oleo-refractometer apply equally well to the butyro-refractometer, except that the actual values are not identical. The author’s experience confirms that of Mansfeld, and shows that, while Muter’s relation is, broadly speaking, correct, there are differences so large between the refractive index found and that calculated on the assumption that this property follows the Reichert value, that the rule cannot be depended upon. The refractive index is a property which is much more nearly related to the iodine absorption, or, in other words, to the unsaturated carbon atoms. Though a very convenient test, it has but little value alone, unless the value is below the average, 46° at 35° C., but in the presence of coco-nut oil and margarine an adulterated butter may give a normal figure. When a butter is adulterated with vegetable oils—e.g., cotton seed—its indications are of some value. It is also useful in detecting coco-nut oil, but its value is chiefly corroborative. A standard fluid (normal fliisstgkeit) is supplied with the instru- ment, and the readings of the scale should be checked from time to time by its use. The point at which the dividing line should lie at 35° C. is marked in the instrument, and the scale should be brought to this point by means of a key just above the prisms. Viscosity.—Killing proposes to take the viscosity of butter fat as a test by running it out of a pipette, marked above and below the bulb, and records the time taken for the melted fat to flow from one mark to another. The instrument must be gradu- ated with butters and other fats of known purity. He gives the following average times of How :— Butter, . 3 minutes 434 seconds. Margarine, ‘ 4 oy £ ee Lard, . f 4, 28 > Beef fat, ‘i F 5 4 “, 33 a Wender uses an apparatus called a fluidimeter. This consists of a U-shaped capillary tube having at one end an enlargement holding 10 c.c., and at the other an enlargement holding 2 c.c. ; the larger bulb is placed higher than the smaller; liquid, there- fore, flows from it. A solution of the fat in chloroform is used ; the upper bulb is filled with this. the solution allowed to flow into the lower bulb, and the time noted which it takes to pass from the lower mark to the upper one on the smaller bulb. The time taken for chloroform to flow is also noted. and this is taken as 100. B52 BUTTER. The viscosity of the fat is calculated by the following formula :— Let V = viscosity of the fat, x =: percentage of fat in chloroform solution by volume, and TT = the time taken divided by the time taken by chloroform, ‘en aa OO a (100-2) The average time for chloroform to fill the lower bulb was ‘20°04 seconds. Wender gives the following values as the mean figures at ‘20° C. (chloroform = 100) :— Viscosity of pure butter, . ; 344-3 margarine, . . 373-2 2”? 2 It does not appear that this test has any greater value than other physical determinations. Behaviour of Butter on Melting.—When butter is melted at a temperature of about 60° C., the fat which flows from the aqueous portion is generally clear and transparent; when mar- garine is melted, the fat is almost always cloudy. This has been used as a test for the purity of butter. It does not appear to depend on any property of the fat, but on the ‘state in which the fat existed in milk, and the method of pre- paring the butter. Butters which have been overworked invari- ably melt in a cloudy manner. Druot has devised an apparatus for observing the behaviour on melting. It consists of a number of cups stamped in tin plate, in which pieces of the samples to be tested, about 14 ‘grammes in weight, are placed. A piece of iron heated to about 60°, and of sufficient thickness to retain enough heat to melt the ‘samples, is placed over the top, and left till the butters are melted. The appearance of the fat is observed, the polished ‘surface of the tin plate materially aiding the observation. This method can only be classed as a rough means of deter- mining the purity of butter. Melting Point of the Fat.—Formerly some importance was attached to the melting point of the fat; this, however, depends to some extent on the method employed in determining it. Butter melts at about 33° C.; and artificial butters are made up to melt at the same temperature. Among other physical properties which have been proposed aare the determination of the heat of combustion, which differs materially in butter and other fats, and the relative transparency to the X rays. These methods are not, however, practical analytical methods. DETECTION OF ADULTERATION. 353 Detection of Adulteration of Butter—The most useful and rapid preliminary test is examination with the butyro-refracto- meter. Any sample showing a refractive index of less than 46° at 35° C. is most probably genuine, but may, however, contain coco-nut oil. The Reichert-Wollny process should next be applied. Any sample requiring less than 20 c.c. for 5 grammes may be taken as adulterated; samples requiring more than 28 c.c. may be passed as genuine, though they cannot absolutely be certified as free from adulteration. Any sample taking a N : bee es volume of bw alkali between the limits given above must be further examined. The Polenske and Avé-Lallemant methods should be employed, and if the results are suspicious the phyto- steryl acetate test should be used. Baudouin’s, Becchi’s, Hal- phen’s, and Wellmann’s tests should be applied. A well-marked reaction with any or all of them will furnish strong presumptive evidence of the presence of margarine containing vegetable oils. The soluble and insoluble fatty acids, saponification equivalent, and especially the mean molecular weight of the insoluble fatty acids should be determined. Coco-nut oil can be readily detected by the figures thus obtained. A high Polenske figure indicates this adulterant. The ratio between the Reichert-Wollny figure and the differ- ence between the insoluble fatty acids and 95°5 is much depressed ; in butter the ratio is about are = 35 (R-W = Reichert-Wollny figure, and I = Insoluble fatty acids); while coco-nut oil gives a value of approximately 075. The mean molecular weight of the insoluble fatty acids in butter is about 259, and varies but little from this figure, while the corresponding figure for coco-nut oil is about 200. The iodine absorption of coco-nut oil is also low, about { per cent.: while butter absorbs about 34 per cent. of iodine. Mercier’s or Hink’s microscopic methods should be used before the presence of coco-nut oil is certified. It is far more difficult to detect other adulterants, if present in small quantities. unless vegetable oils are detected. Genuine butters which are below the average in the Reichert figure give high insoluble and low soluble fatty acids, a high iodine absorp- tion, and a low percentage of potash absorbed. In the few samples that the author has examined the mean combining weight of the insoluble fatty acids has not been se high as would be expected. Thus the mean combining weight of the insoluble fatty acids is about 25, while the mean combining weight of the insoluble fatty acids of most adulterants is about 277. The aR 354 BUTTER. Valenta test is also useful, and the density may be used as a corroborative test. Margarine.—It is advisable to calculate from the mean figures yielded by genuine butters and margarines the apparent per- centage of margarine present. If the percentage thus calculated from the mean combining weight of the insoluble fatty acids, the Valenta value, and the density be less than that calculated from the other determinations and, at the same time, the iodine absorption and refractive index are slightly high, it is probable that the butter is genuine. If the contrary is the case, and the apparent percentages from all the methods give approximately the same value, it is probable that the butter is adulterated, especially if the Avé-Lallemant method shows adulteration. If, in addition, the colour tests for vegetable oils have given distinct reactions, the probability of adulteration is strengthened. Though in the present state of science it is not possible definitely to certify many cases of small amounts of adulteration, for dairy control work the task is much simplified. The samples which must be regarded as suspicious can be reported as such, or even as adulterated, with a high degree of probability, and it will be frequently possible to trace such samples to their origin, by examining the fat of the milk of the cows which yielded the butter. Influence of Keeping on the Analytical Properties of Butter.—When butter is kept and becomes rancid very pro- nounced changes take place in the composition of the fat. These may be classed under two heads—hydrolysis and oxidation. If butter fat be kept in the dark and out of contact with the air, it keeps indefinitely without change; but in the presence of light and air it becomes oxidised. The general course of change may be roughly indicated thus— (1) The fat is partly hydrolysed into fatty acids and glycerol. (2) The glycerol is oxidised to fatty acids of low molecular weight (3) The unsaturated acids are oxidised, forming hydroxy-acids. The general effect of these changes is— The volatile and soluble acids are increased, the soluble in greater pro- portion than the volatile. The insoluble acids are decreased. The iodine absorption is lowered. The density and refractive index are increased. The potash absorption is increased. If the butter has been kept in its natural state, the butter fat obtained on melting may have properties differing materially from those indicated above, owing to the solubility of some of the products in the water still left in the butter. The soluble and volatile acids in the filtered fat may be lowered from this cause, and the insoluble acids increased, CHANGES ON KEEPING. 355 The change is not very rapid, and in the course of several weeks the changes are often not very pronounced. Bell has recorded the following figures for the changes in the insoluble fatty acids; the butter in this case was kept for the times indicated :— No. of weeks kept, . e- 12 7 7 6 8 6 Before keeping, per cent., . 87-30 87-80 85-50 87-40 87-72 87-65 After - rs - 88-97 90-00 85-72 87-97 88-40 88-00 Vieth has made analyses showing the change in the insoluble fatty acids produced when butter fat is kept. In each case about a year had elapsed between the two analyses. Percent. Percent. Percent. Per cent. Original insoluble fatty acids, . 87-43 88-33 87-61 87-72 Insoluble fatty acids, after keeping, 85-07 Sony S441 83-82 The same observer has also examined old butter fat and old butter (kept for about ten years) which had not been previously analysed, The old butter fat was divided into two portions—one, com- pletely bleached, contained 83°52 per cent. of insoluble fatty acids ; and the other, which still retained a trace of its natural colour, vielded 83°90 per cent. The results with the old butter were as follows :-— Lower portion, . é . 89-28 per cent. insoluble fatty acids. a3 3 washed, . 89°33 ,, ” ” Upper portion, . ‘ » Hoot ,, ss - Allen and Moor have examined two samples of butter which had been kept for five and a half years. The following table gives their results :— TABLE LNXNIII, Fresh. Fresh. Old. 1 & a | ! a Density aus (in glass), 0-S640 | 0-8634 | 0-8696 (08730 0-8641] .. a5 Reichert-Wollny, . | 22-51 | 14-43 | 12-02) 12-02 | 24:55 | 22-48 Potash absorption, 221-6 | 219-9 | 225-5 | 228-8 | 220-9 | 233-3 Soluble fatty acids, : percent., . : t44 3-82 5-66 | O80 4-68 5-89 Insoluble fatty acids, per cent., P - | 90-44 1 90-73 ' DU- ! Jodine absorption, . oe 30:01 27-17 25-08 = © = } S 90-10 | 85°75 Bs 25°57 * This figure was determined hy the author on a duplicate sample. 356 BUTTER. Clayton has analysed a butter which in 1879 gave in Hehner’s hands 87°75 per cent. of insoluble fatty acids. His results were :— TABLE LXXXIV. Density P Melting 100° Insoluble Soluble Reichert- Point. 55° Fatty Acids.| Fatty Acids.) Wollny. (in glass). Per cent. Percent. c.c. January, 1895, ade 0°8742 . 85°72 ins 22°36 October, 1897, 33° C. ba i 7°36 See Potash Iodine Maumené ai absorbed. | absorbed. figure. Rancidity. Milligrms. | Per cent. January, 1895, iy 25°68 ae et October, 1897, 234-7 25°09 22° ©. | 100 grammes required 160°3. c.c. normal alkali. is Besana has examined twenty samples after keeping for various periods of time; he estimated the Reichert-Wollny figure (Table LXXXYV.). TABLE LXXXV.—Tue ReicHert-WoLLtny FIGURE OF BurrTERs. No. of days Reichert-Wollny Figure. between first . and second Difference. test. Fresh Butter. Rancid Butter. 173 27°70 27:42 — 0:28 171 27°28 26°98 - 0:30 170 27°50 27°28 — 0°22 169 27°51 27°64 + 0:13 164 27°43 27:75 + 0°32 162 28°49 28°30 - 0:19 161 27°90 27°65 — 0°25 160 27°54 27°40 - ult 157 21°72 27°31 — 0-41 157 28°49 27:97 ~ 0°52 134 29°15 29°40 + (25 131 29°48 28°74 ~ 0°74 107 29°48 28:96 - 0°52 107 29°70 29°18 - 0°52 84 29°40 28°85 - 0°55 84 29°36 28°74 - 0°62 79 27'87 27°42 — 0°45 47 28°08 28°30) + 0:22 46 27°86 27°75 - O11 46 28°85 28:96 + O11 ' CHANGES ON KEEPING. 357 Vieth has examined a butter which had been kept more than ten years; the fat then yielded the following Reichert-Wollny figures—26'2, 25°6, 25°77, and 21°2 c.c. on different portions. He has also examined butter fat which had been kept for eighteen mouths. The results were :— Fresh, . . 29°2 c.c. 29:9 c.c. Old, . . 30-4 ce. 29-5 c.c, (determined by the author). Another example of butter fat well protected from the light gave in July, 1888, from 31°6 to 32°] c.c. of - alkali, In— October, 1888, it gave 31°8 c.c. January, 1889, ees ey May, 1889, » a2 yy September, 1889, » «= 1855 December, 1889, 33. 82'S gy April, 1890, 93 O20 59 July, 1893, x7 ~—« 83D 45 The last figure was determined by the author; the others by Vieth. It ig seen from the figures quoted above that the analysis of butter which has been kept for any length of time is a matter of considerable difficulty. Though in butter fat the volatile acids do not show any diminution, but rather an increase (due pos- sibly to the oxidation of the glycerol), in butter the reverse is usually the case. It is by no means improbable that, besides the solubility of these in the water contained in the butter, a portion is destroyed by the action of micro-organisms. The most reliable datum would seem to be the determination of the volatile acids on the butter itself without separation of the fat, subsequent determination of the fat, and calculation of the Reichert figure on the actual fat present. The potash absorption does not appear to undergo much change. The phytosteryl acetate test may be applied to rancid butters. Detection of Rancidity in Butter.—The amount of free fatty “10 any higher figure indicates partial hydrolysis. Soltsien recom- mends that the fat be steam distilled, treated with alkali in excess, and again steam distilled. Wellmann’s reagent is added to the distillate, and ammonia in excess; and a blue colouration in from half to one minute indicates rancidity. Buttermilk.— Definition.—The term buttermilk is applied to the aqueous portion left after churning. It differs only slightly in composition from skim milk. As the cream used acids in fresh butter does not exceed 5c.c. — acid per 100 grammes, 358 BUTTER. for churning is usually slightly sour, the buttermilk contains appreciable amounts of lactic acid; it will also contain water or any other substance which has been added during churning. There is, in suspension, a considerable amount of Storch’s mucoid protein, which may be removed by passing it through a cream separator, when it is deposited on the sides of the drum. Composition.—The following composition of buttermilk from sweet cream is given by Storch :— Water, . : : 2 . 89-74 per cent. Fat, . ‘ A : 2 z . 121 5 Milk-sugar, ‘ ‘ ‘ ; - 4:98 35 Protein, . e . ji ‘ - 3:28 i Ash, ‘ . : F f « -OF79- 33 Buttermilk from ripened cream has the following composi- tion :— TABLE LXXXVI. Authority, .. Storch. Vieth. Fleischmann. Per cent. Per cent. Per cent. Water, ‘ ; : 90°39 91°24 Fat, . ‘ 0°31 0 50 0°56 Milk-sugar, ‘ , 4°58 4°06 4-00 Lactic acid, P * (?) 0°80 Protein, 5 ? : 3 37 3°60 3°50 Ash, . . : 0°81 0°75 0-70 The author finds the following figures in buttermilks prepared in different ways :— TABLE LXXXVII. Sour Sweet . Separated Cream. Cream. Milk. Milk. Specific gravity, 7 1:0314 1-0331 1-0329 10355 Water, . ‘ é 91-61 90-98 91-13 90-77 Fat, 5 3 5 0-50 0°35 0-70 0-10 Sugar, 7 . E 3-40 4:42 3°65 3°93 Lactic acid, A 3 0-50 0-01 0-76 0°56 Protein, . . : 3°30 3-51 3°28 3°65 Ash, 5 ‘ Z 0-65 0-73 0-68 0-79 Variations of Fat.—The author has found the amount of fat in buttermilk to vary from 0°15 per cent. to 5°60 per cent. ; the last percentage is very unusual, and it is rare to find even BUTTERMILK. 359 as much as 2°0 per cent., percentages higher than this denoting that the churning has been inefficiently carried out. Ash.—The following composition is given by Fleischmann to the ash of buttermilk :— TABLE LXXXVIIL. Potash, K,0, . . a . . 24°53 per cent. Bede NEO, a ow aw 4 TE Lime, CaO, . . - 5 5 - 19°73 ‘9 Magnesia, MgO, . . . - 3°56 43 Phosphoric acid, P:0s,« ‘ 7 a . 29°89 ‘3 Chlorine, Cl, é ‘ - 13°27 5 Iron oxide, ie. a. ce 7 i . 0°47 ” 102:99 4 Less oxygen = chlorine, ~- « 2°99 4 100:00 os Buttermilk has usually a slightly acid flavour; it does not, however, taste quite like sour skim milk, but has a distinctive smell and flavour of its own; it is not known to what this is due. On microscopic examination it is seen that the fat left is not entirely in globules; there exist many small nuclei consisting of two or more fat globules. Chemical Control of Churning Operations.—The fat in the buttermilk from each churning should be estimated. Usually less than | per cent. of fat may be considered satisfactory, but if sweet cream is churned it is difficult always to keep within this limit. Any percentage of fat above 2 must be considered unsatisfactory, and the cause should be enquired into. This may be due to the use of cream which is too thick, mixtures of cream of different consistency and age, too high a temperature, or too rapid churning. The fat in the cream to be churned should also be estimated. It has been found that cream containing from 25 to 30 per cent. of fat gives the most satisfactory results. If the cream contains more than 40 per cent. of fat, the buttermilk is very high in fat, and a larger percentage loss is obtained. The weight of fat in the butter plus the weight of fat in the buttermilk should come within 2 per cent. of the weight of fat in the cream used. If a larger difference is found, a needless loss of fat is taking place, and the cause of this should be ascer- tained. Table CNLI. (Appendix) gives the weight in pounds of butter which may be expected to be produced on churning cream varying in percentage of fat from 15 to 50. 360 BUTTER. An approximation to the amount of butter in pounds that may be obtained from milk by churning the separated cream ean be obtained by subtracting 0°1 from the percentage of fat, multiplying the difference by <5, and by the number of gallons of milk. Estimation of Water and Salt in Buttermilk. — It sometimes happens that when churning both salt and water find their way in the buttermilk; when the buttermilk is to be sold, it is important to be able to estimate rapidly both the proportion of water and of salt. It was found that chlorides could be titrated in milk with 10 silver nitrate solution, using potassium chromate as indicator, and that 10 ¢.c. of milk took on an average 3°45 c.c. al silver solution, with extremes of 3°35 c.c. and 3°6 c.c. in nine samples. It was further found that the number of c.c. of x silver solution for 10 c.c. of milk could be deduced with considerable accuracy by multiplying the aldehyde figure (obtained with strontia) by 0°171, and subtracting this quantity from the quantity actually used ; the remainder was a measure of the sodium chloride. A series of determinations showed that 1 gramme of sodium chloride added to 100 c.c. of milk raised the density by 0°00735, and by multiplying the amount of salt found by this figure the increment of density due to the addition is deduced, and sub- tracting this from the density found, the density of the milk is obtained. From this last figure and the fat the solids not fat can be calculated, and from this the amount of added water roughly deduced. The method is :—Hstimate the specific gravity, fat, and alde- : sit tse ¢ Neos hyde figure as usual; titrate 10 c.c. of buttermilk with 10 silver nitrate, using potassium chromate as indicator, till a reddish colour is produced. From the volume of silver nitrate used subtract the aldehyde figure x 0°171, and multiply the residue by 0°0585, the product is the percentage of salt; multiply this by 0°00735, and subtract the resulting figure from the specific gravity; the percentage of added water, if present, is calculated from the fat, and the corrected specific gravity in the same way as the extent of watering of milk is deduced (p. 173). It is sometimes asserted that a certain amount of water (20 or 25 per cent.) is allowed to be added to milk or cream for churning purposes. This view, however, appears to be quite incorrect ; the addition of “‘ breaking ” water does not appear to be recognised BUTTERMILK. 361 by any statute, and if buttermilk is to be sold there is no reason why it should contain any added water. It is probable, how- ever, that should a sample of buttermilk taken under the Sale of Food and Drugs Acts be found to contain a small percentage of added water, the Public Analyst would advise his authority that it is a custom to add water during churning, and a prosecution for the addition of small percentages is improbable. The Use of Starters in Butter-making.—The acidity of the cream should be determined before churning, if ripened cream is used. An acidity of about 60° will generally vield good results. In order to ensure that a good flavoured butter is produced, it is necessary that the proper organisms are present; this is best ensured by pasteurising the cream, and after cooling adding a starter, which has been found to produce a good flavour. The starter provides an enormous excess of lactic acid bacteria, which at the ripening temperature develop rapidly and overgrow any other organisms that may have found entrance. A starter is prepared by sterilising 1 to 2 litres of milk, adding a tube of one of the preparations on the market, which are pure cultures of lactic acid bacteria, and keeping the milk at about 70° F, till thick. A rough, but usually very successful, method is to allow a specimen of milk, which develops a clean acid taste on keeping to stand at about 70° F, till sour. The lactic acid organisms are very active at this temperature, and, as they tend to overgrow any others that may be present, a fairly pure culture is the result. Starters may be kept going by adding to 1 to 2 litres of milk that has been sterilised a little of a previous starter, and keeping at 70° F. 362 CHAPTER VII. OTHER MILK PRODUCTS. ContEents.—Cheese—Rennet—Classification of Cheeses—Composition— The Ripening of Cheese—Analysis of Cheese—Adulteration of Cheese —Other Products derived from Milk. Cheese. CHEESE is prepared by the action of rennet on milk; this separ- ates it into whey and curd; the curd is finely divided, pressed to separate the whey and to consolidate it, and, usually, salted. From this, cheese is produced by ripening, which is due partly to the action of micro-organisms and fungi, partly (as Babcock and Russell have shown) to the action of an enzyme natural to milk. Action of Rennet.—The action of rennet is to split up the casein into a dyscaseose, the calcium compound of which is insoluble and which forms curd, and a soluble caseose; the insoluble curd carries down with it a large proportion of the fat. Composition of Curd and Whey.— The following table will show the distribution of the various constituents of the milk when made into whey and curd :— TABLE LXXXIX. Milk. Whey. Curd. Per cent. Per cent. Per cent. Water, ‘ ‘ ° 87°30 80°80 Fat, . a ‘ ‘ 3°75 0°30 3°45 Milk-sugar, 3 2 4°70 4°40 0°30 Casein, 3 5 3:00 0°40 2°60 Albumin, . ‘ F 0:40 0°40 trace Ash, . : i; ‘ 0-75 0°60 O15 The following is the composition of whey according to various authorities :— TABLE XC. Fleischmann. Gone. Smetham. ee . Per cent. Per cent. Per cent. Per cent. Water, . ‘ 93°15 93°38 93°33 93:00 Fat, ‘ ‘ 0°35 0°32 0:24 0:09 Milk-sugar, . 4°90 4:79 5:06 5°45 Protein, . ‘ 1:00 0°86 0°88 0:92 Ash, é . 0°60 0°65 0:49 0°54 WHEY. 363 The author has found the fat in whey to vary from 0°04 per cent. (from skim milk) to 1°35 per cent., and the solids not fat to lie between 6 and 7 per cent., averaging 6°6 per cent., which contain— Milk-sugar, . ‘ . 5-0 per cent. Protein, 5 . F ve oe LO” 4x Ash, : 06 4, On adding an acid to whey, a slight protein precipitate (which is difficult of filtration) is obtained. On heating the acid whey, a soft curd of little consistency is formed; this substance 1s a commercial article on the Continent. The composition of the whey and the precipitated curd (after acidifying and boiling) are given :— TABLE XCI. [ By Fleischmann. By Bochicchio. Whey. Precipitate. Precipitate. Per cent. Per cent. Per cent. Water, ‘ F ‘ 93°31 68°5 i Fat, % é ‘ a 010 31 5°22 Milk-sugar, . . : 5°85 32 3:97 Lactic acid, . : . ae 0:8 ne Protein, . ‘ 5 0:27 228] 18:72 Ash, . ‘ ‘ ‘ 0:47 2S 62 if On boiling whey without acidifying. a precipitate of a similar nature also occurs ; this appears to consist of coagulated albumin. Cheese is sometimes prepared by allowing the milk to become sour spontaneously, salting and pressing the curd, and allowing it to ripen. This variety of cheese is not considered of such good quality as rennet cheese. Fleischmann gives the composition of the whey thus obtained as follows :— Water, ; : ; 93-13 per cent. Pat, s : i Z " Z ‘ (P12 a Milk-sugar, . ‘ : ‘ 4:38 Fe Protein precipitated by acetic acid, OAT, i ee tannin, 0-59 x Ash, . i 5 4 OS2 Difference (lactic acid ”), 0-49 Vieth has shown that whey prepared in this way undergoes. alcoholic fermentation much more readily than rennet whey. 364 OTHER MILK PRODUCTS. Rennet.—This substance is an enzyme produced in the stomachs of mammals; it occurs in the human stomach, and the curdling of milk when ingested is due to this; it is especially abundant in the young while still suckling. Preparation.—It is usually prepared from the fourth stomach of the calf. The stomachs are dried and kept for some time ; they are then cut up into small pieces and macerated in a 5 per cent. salt solution, usually containing boric acid, for some days ; to the solution a further 5 per cent. of salt is added, and the liquid filtered; this forms extract of rennet. By adding more salt, the rennet is precipitated, and “rennet powder” is pro- duced; this consists, essentially, of the ferment, together with other organic matter, and a considerable amount of salt. Properties.—Rennet acts on casein only in neutral or acid solution, and its properties are destroyed by alkalies. Like all enzymes it has an optimum temperature at which it acts best ; this has been found by Fleischmann to be 41° C. (105°8° F.). He gives the following table as showing the relative proportion of milk coagulated in a given time by the same quantity of rennet at different temperatures :— TABLE XCII. ; | Temp. C. Proportion. Temp. C. Proportion. Temp. C. Proportion. 20° 18 36° 89 ‘ 44° 93 25° 44 37° 92 | 45° 89 30° 71 38° 94 | 46° 84 31° 74 39° 96 | 47° 78 32° 77 40° 9S 48° 70 33° 80 41° 100 49° 60 34° 83 42° 99* f 50° 50 35° 86 43° 96 i At the optimum temperature, and for several degrees on either side, the curd produced is very firm; at low temperatures, 15° C. to 20° C., the curd is quite soft and flocculent; and when the temperature is raised to 50°, the curd again becomes very soft. By heating rennet to temperatures much above 60° C, (140° F.) it rapidly loses its properties, and it also loses strength by long keeping. The action of rennet is affected by the acidity of the milk; the larger the amount of acid, the more rapid the action; the * Given as 98 in original, but from the experimental data it appears that 99 is more correct. RENNET. 365, addition of water to milk causes it to be coagulated more slowly by rennet and the curd is less firm. By heating milk, the action of rennet is delayed, owing to the removal of some of the soluble calcium compounds. By the addition of soluble lime salts, the milk will be curdled by rennet in the usual manner. Alkalies destroy the power of rennet to curdle milk; borax acts as an alkali, boric acid being inert to rennet. Testing of Rennet.—It is important to know what the strength of rennet preparations are—i.c., the amount of milk that will be curdled by 1 part in a definite time at a definite temperature. This may be estimated as follows:—5 c.c. of a rennet extract or 0°5 gramme of a rennet powder are made up to 100 c.c. with distilled water. After thorough mixing, 1 c.c. is measured out by means of a pipette and added to 100 c.c. of separated milk of acidity 20°, which has been brought to a tem- perature of 35° C.; the milk and rennet solution are immediately well stirred and the exact time at which the rennet was added noted. The milk should be contained in a beaker, which is placed in a water-bath kept at 35° C., and gently stirred with a thermometer till it is found, by the path becoming visible, that the milk has coagulated ; the exact time which has elapsed from the addition of the rennet till the coagulation sets in is noted. The strength of the rennet—7.e., quantity of milk that will be coagulated by 1 part in forty minutes—is calculated by the following formula :— Let = quantity of milk coagulated. p = proportion between milk and rennet taken. ¢ = the time. 4 Then gs ats t The value of p is 2,000 when 5 c.c. was diluted to 100 c.c. and 1 c.c. taken, and 20,000 when 0°5 gramme was taken. If the time taken is less than five minutes, or more than ten minutes, it is advisable to make another determination, using a smaller or larger proportion of rennet to milk. Classification of Cheeses.—Cheeses may be divided into the following classes :— 1. Soft Cheeses.—These are obtained by coagulating the milk with rennet at a low temperature (below 30° C. or 86° F.). The period of coagulation lasts a long time. As representa- tive of these cheeses the following kinds may be mentioned :— Gervais and Pommel made from cream; Brie, Camembert. Pont l’Evéque, and Bondon (or Neufchatel) made in France; and Stracchino made in Italy. 366 OTHER MILK PRODUCTS. _2. Hard Cheeses.—These are obtained by coagulating at higher temperatures (30° C. or 86° F. to 35° C. or 95° F.); they may be again divided as follows :— (1) Cheese made from milk and cream—Stilton. (2) Cheese made from whole milk—Cheddar, Cheshire, Dunlop, and Wensleydale made in England ; Port de Salut made in France ; Emmenthaler or Gruyére made in Switzerland, Edam in Holland, and Gorgonzola and Cacio Cavallo in Italy. (3) Cheese made from partially skimmed milk—Parmesan in Italy ; Derby, Gloucester, Leicester, and, sometimes, Cheddar in England; Edam (usually made in this way) in Holland, and Gruyeére in Switzerland. Skim milk cheese and cheese made from skim milk enriched by margarine are also made. A famous cheese, known as Roquefort, is prepared from sheep’s milk; Besana has shown that many sorts of cheese may be made from sheep’s milk. Goat’s milk ig also employed in cheese manufacture, but these cheeses are not important articles of commerce. In addition to rennet cheeses, cheese made from the curd precipitated by warming milk which has been allowed to become sour is also used. The only cheese thus made in England is cream cheese; frequently an acid is added to the cream instead of allowing lactic fermentation to take place. A Swiss cheese, Glarner, and the German caraway cheese come under this category; the latter is mixed with caraway seeds. Composition of Cheese.—But little is known of the composi- tion of cheese. Most of the analyses made have included only water, fat, ash, and total nitrogenous substances either by differ- ence or by estimation of the nitrogen and multiplication of this by a factor. In very few cases has the separation of the nitro- genous matters been attempted, and it is doubtful whether, where this has been done, much real information as to the character of the products has been obtained. The chemical knowledge of cheese must be pronounced to be in a much less satisfactory condition than that of other milk products. The following tables (XCIII. to XCVII.) will give the proxi- mate composition of various cheeses; they will be useful as show- ing the most striking differences. Thus soft cheeses contain large amounts of water, and small percentages of fat and protein; cheeses made from whole milk contain an amount of fat at least equal to the protein, while skim milk cheeses contain usually less fat than protein; in cream cheeses the fat greatly exceeds the protein :— ’ COMPOSITION OF CHEESE. TABLE XCIII.—Cream CHEESEs. 367 Authority. Water. Fat. =, Protein. Pe ue | Ash. | uC soa l. English cream cheese made without rennet. i Per veut. Per cent. Per cent. Per cent Per cent. Vieth, 30°66 62:99 | 4-94 0:26 | 115 Smetham, 20-56 80:03 = = 2-99 Q:57 0°83 Pearmain & Moor, 57:6 39:3. | 19-0 7 3-4 Author, 26-50 67-00 | 405 O-71 0-37 Vieth found the insoluble fatty acids of the fat to be— When fresh, 87-31 per cent. After 1 month, 87°12 55 Sg ee bag 88-2 95 sn Ort C8 87-96, 77 4 ceo 87:58 ”> 2. Gervais cheese. Per cont. Per cent, Percent.» Percent. Per cent. Vieth, . . ) 42-32 49-18 175 | O27 | usd | Stutzer, . ; | 44-84 36°73 15-48 | 5 2-95 | Author, 41-0 49-5 | 41 112 05 3. Pommel cheese. | 2. | Author, : | 44-9 45-5 | hee 1-16 | TABLE XCIV.—Sorr CHEESES. oe ee Authority. Water, i: Fat. Protein. | es Ash. Per cent. | Per cent. | Per cent. | Percent. | Per cent. 1. Brie. Duclaux, . ‘ - | 50°04 27°50 18°32 4:12 2. Camembert, Duelaux, . 45-24 30°31 19°75 nee 4:70 Stutzer, 50°90 27°30 18°66 Pe 3:14 Cameron & Aikman, 51°30 21°50 19°00 aaa 4°70 Letfmann & Beam, . | 51°40 21-00 18:90 we 4°70 Pearmain & Moor, 45°65 2295 23-10 oh 4°25 Muter, AS‘7S 21°35 19°71 36 9°30 3. Neufchatel (or Bondon). Fleischmann, . ‘ 345 41°9 13:0 70 3°6 Pearmain & Moor, . | 39°5 244 9°4 ee 0-7 Muter, . 7 55°20 20°80 15°38 164 6:98 4. Stracchino, Konig (average), . | 39°21 33°67 29°32 eee | 3°80 368 OTHER MILK PRODUCTS. TABLE XCV.—Harp CuHEEsss. Authority. Water. Fat. Protein. fae Ash. Per cent. | Per cent. | Per cent. | Per cent. | Per cent. 1, Stilton (made from milk and cream). Pearmain & Moor, . | 20°30 44:00 23°70 — 2°75 Cameron & Aikman, | 35°20 33°97 24:12 wet 3°56 Muter, . 7 . | 28°60 30°70 35°60 1:08 4:02 Konig (average), 32:07 34:55 26°21 3°32 3°85 2. Cheddar. Pearmain & Moor, .| 27°19 30°76 29:20 4°66 (Ameriean) 3 is 33°90 29°05 27°37 ‘| (English) Cameron & Aikman, | 27°20 32°05 36°60 4:15 (American) ae 3 28°09 22°52 45°75 “is 3°64 (English) Muter, . : . | 29°70 30°70 35-00 0-90 3°70 (American) ” 33°40 26°60 34°17 153 4°30 (English) Kénig (average), 33°89 33°00 27°56 1:90 3°65 3. Cheshire, Smetham, ‘ 39°33 30°80 23°70 2°43, 3°60 Pearmain & Moor, 34°70 33°30 26°10 Pe 4°30 Leffmann & Beam, . 30°4 25°5 36'1 4:80 4, Gruyére (or Emmenthal). Fleischmann, 36:1 29°5 28:0 3°3 3:1 Duclaux, . . 36:00 29:29 30°84 mae 3:87 Stutzer, ‘ F 33°01 30:28 31°41 . 5:30 Pearmain & Moor, 31°45 30°20 30-00 F 4:20 Cameron & Aikman, 37°34 26°47 31:33 ai 3:42 Muter, . ‘ . | 33°20 27:26 33°49 1:35 4°70 Leffmann & Beam, 32-0 28°0 35°1 : 48 Konig (average), 36°49 28°01 30°83 re 3:95 5. Cacio Cavallo, Sartori, _. ‘ 19°76 36°71 34:12 3°70 5:60 Spica & De Blasi, 23°67 25°49 29°25 17°35 4°24 COMPOSITION OF CHEESE. TABLE XCVI.—Sxim Mitx CHEESEs. 369 Authority. Water. Fat. Protein. den ae Ash. Per cent. | Per cent. | Per cent. | Per cent. | Per cent. 1. Dutch. Duclaux, . ‘ 37°31 24-41 32-50 5-69 Pearmain & Moor, 32-90 17:78 30-80 6:40 Konig (average), 37:35 24-61 32-40 oe 5-65 Muter, . F 42-72 16:30 28:27 1:35 11-36 2. Gloucester. | Cameron & Aikman, 28-62 23°67 43-54 447 | Pearmain & Moor, 35-25 | 25-80 | 30-05 4 4-80 | Muter, é 37:20 22-80 33-64 1-80 4-56 3. Grana, Duclaux, 32-56 21°75 42-27 ar 507 | Konig (average), 31-33 23-90 35:3 4:17 526 4, Parmesan. : Duclaux, 30-09 26-04 38-42 a a5 Konig (average), 31-80 19-52 41-19 1-18 6-31 | Pearmain & Moor, 32-5 WL 43-6 62 ¢ Cameron & Aikman, 27:56 15-95 44-08 72 5, York. | (a soft cheese). | Muter, ‘ . 63-64 15-14 18-50 1-80 0-92 Vieth, OS-44 12389 14-50 2-88 1-29 Author, 70:5 10:8 13:8 O85 Ae]. | Besides these cheeses, which are all made from cow's milk, the famous Roquefort cheese, made from sheep's milk, must be mentioned. Its composition is— TABLE XCVII. : | tie Authority. Protein, HVE. I ash, Konig (average), 36°85 30°61 2525 190 | 539 | Pearmain & Moor, 29-6 =| 30:0 28-3 ae oy OO Leffmann & Beam, 265 32-3 B20. any ae [oda | Muter, 21°56 35-06 2452 O72 | 10-24 In the above analyses the figures under the term “ proteins” include true proteins and their products of ripening, and, fre- quently, also such products as lactic acid. : Proteins in Cheese.—Besides the analyses given on pp. 367 to 369, the following, in which an attempt has been made to distinguish between the various constituents, may be ae OTHER MILK PRODUCTS. 370 vi 68-0 | G69-LT | 99-0 G8-0 | Shes | SOG | LOLT | LEE | * -_ 2 Bacon i 6L0 | SLT | PLT L8-0 | 99-9 see | LeLE | Lee | * = empaeae “ 96-0 | 08-4 68-0 £9-0 | 19-02 LLG | 69-98 | TE-9% ; > argdnay) i 11-0 | 6L:€ $L-0 G-0 | 061% | 8S | 9-93 | b3-TF : eel > IL-0 | 0&4 GL-0 €9-0 | 86-02 | SIF | LEIS | 69-L8 | * ; we ich TUUTeUs TE ZO | ST8 98-0 1:0 | &6-FT | GLE | €8-08 | 38-0F | * (edt) ay ‘Tzzouoyy ‘ossnyy | 60-0 | F9-T $10 Sel | 96-71 ers | 19s | ZO-Ge | * * — ‘(yseaz) ourgoorsyg “quad 129g | “quad Jag | ‘queo Jog | ‘qued Jag | ‘quad Jog | 4Ua0 Tag | “Ua Tag | "U29 Jog “spunod “» | medium $3 Cow, . te) 0 medium many © . ne | v. few 5 Rabbit,*, many many few few | v.few | v.few | v. few | v. few Ass, 0 y.few | v.few many . medium) medium v. many rh Mare, . (a) re medium medium | few many | many ~ Sow, . 0 to) v.few | v.few | v. few | medium v.many| many Bitch, . tr) 0 many | many | medium 55 \. few | v. few Cat, Co) te) few few 55 few % ‘9 Mouse,*| many | many is os s v. few as * The milk of the rabbit and mouse contained globules up to 0-0181 mm. in diameter. COMPARISON OF MILKS. 391 (b) Composition of Fat,—The following table (CVI.) gives the comparative figures for the composition of the fat of various mammals :— “TABLE CVI.—Properties or MamMatian Fats. \ : ‘ Zeiss Name ot | Melting | solidifying | Ryicnen | Insoluble | Refractive Mammal. Point. Point. Figure. ixeitle: anaes i A 7 Per cent. Woman, . 32° 22°5° 1-42 oe 51°9° Ewe, . 29° 12° 26°7-32°89 oes Goat, F 305° 31° 26 1-28°6 Buffalo, . 38° 2v° 25°4-39 is ans ae 43°7°-49°0° Cow, e wii i 20°0-34 86 to 90 { meande Rabbit, . ren fae 16°06 Ass, . s sas aa 13°09 Mare, , ats — 1122. Sow, , 25° Ie? 165 Bitch, : a Sey Let Cat, . ext ani 4 40 Mouse, a seen ' 207 sie hie A sample examined by Allen contained 5°06 per cent. Porpoise of volatile acid, having a mean combining weight of ve 104°7, and agreeing with valeric acid (m.c.w. 102) in its properties. t : Sugar.—The author has proved that the sugar of the milk of goat, the ass, and the gamoose (in summer) contains milk-sugar. With Pappel the author obtained analytical figures which showed that the sugar of the milk of the gamoose in winter differed from milk-sugar, and with Carter that the sugar of human milk did not correspond with milk-sugar. It is probable also that the sugar of mare’s milk is not identical with milk- sugar. Denigés and also Landolf state that all milks contain lactose, but that other sugars are present in addition. Proteins.—But little is known of the proteins of milk. It appears probable that the curd-forming milks contain the same proteins as cow’s milk. The milks which do not form curd may differ in their proteins, but it is possible that the different reaction with rennet is due to a deficiency of lime, or to an alkaline reaction. The following milks have an alkaline reaction to litmus :— Human milk, the milk of the mare, ass, rabbit, sow, and cat. Composition of Milk.—Table CVII. gives the mean com- position of the milk of different mammals. Of these milks those of the cow, goat, sheep, buffalo, mare, ass, and, in some countries (e.g., Spain), sow are used for human 392 THE MILK OF MAMMALS OTHER THAN THE COW. consumption, and, with the exception of that of the sow, are worthy of a more detailed notice, Human milk, the natural food of infants, will also be dwelt on. TABLE CVII.—Composition or MamMaLiaNn MILK. Water. Fat. Sugar. Casein. | Albumin. Ash. Per cent. | Per cent. | Per cent. | Per cent. | Per cent. | Per cent. Cow, . «+ + 87°32 75 4°75 3:00 0°40 075 Goat, | 1. 1 | 8604 | 4°68 | 4:22 | 349 | 0-86 | 0-7 Ewe, 2 « « 79°46 8°63 4:28 5:23 1°45 0°97 Buffalo, . . 82°63 761 4°72 354 0°60 0-90 Woman,. . 88-2 33 6S 1:0 05 0-20 +, Mare,. . . . | 89°80 1:17 6°89 St 0°30 Ass, . . . «| 90°12 1°26 6°50 82 1 0-34 0°46 ———-,- ad Mule,. . . . | 91°50 1°59 4°80 164 0:38 Bitch,. . . . | 75°44 9°57 3:09 610 : 5-08 0°73 Cat, . . . . | 81°63 3:33 4°91 3:12 | 5:96 0°58 —-_--,--—_-—“—“ Rabbit, . . . | 69°50 10°45 1:95 15 54 2°56 Liama, « » » 86°55 3°15 5°60 | 3:00 | em 0°80 Camel, . . .| 8657 | 307 | 5:59 4°00 0-77 Elephant,. . . | 67°85 19°57 8°54 3°09 0°65 Sow, . . . | 8404 4:55 3°13 7:23 1:05 Porpoise,. . . | 4111 | 48°50 1°33 1119 0°57 Whale, . . .| 48°67 43°67 711 0°46 Human Milk—Appearance.—In appearance human milk has usually a chalky white, somewhat watery appearance; some specimens, usually those high in proteins, Have a marked yellowish tint. A red coloration, due to blood, has been noticed by Carter and the author. Properties.—The fat globules, according to Pizzi, vary in size from 0°009 mm. to 0°0009 mm. Carter and the author have observed also that they are, on the whole, smaller than those of cows’ milk. The taste is rarely, if ever, sweet, but rather saline. The reaction to litmus paper is almost always alkaline. The acidity is about 30°. Composition.—Human milk appears to be more variable in its composition than that of the cow. This is probably due to the fact that, while the cow is forced to adopt regular habits and leads a life which is very regular, the many occupations and duties of woman do not permit of this. Table CVIII. gives the mean composition of human milk according to recent observers. HUMAN MILK. 393 TABLE CVIII.—Mean Composition or Human MILK. Observer. Water. Fat. Sugar. | Proteins. | Ash Per cent. | Per ceut.| Per cent. | Per cent. | Per cent. Leeds,* . . ‘ 86°69 4:16 6-95 2-02 0-22 Pfeiffer, ‘ ‘ ‘ 88-22 3-11 6:30 1-94 6-19 Luff, . ’ ‘ ? 88-51 2-41 6-39 2:35 0-34 } Johanssen, . . F 3-21 4:67 1:10 Carter and Richmond, . 88-04 3-07 6-59 |. 1:97 0-26 Lehmann, . F 3 87:3 3-4 64 17 (2 Camerer and Sdldner, . 88-07 3-24 6-33 1-69 U-2t Szilasi, ‘ ‘ 2 87:24 3-38 6-97 2-20 0-20 Backhaus, . . 2 87-41 4-02 G71 1-62 O25 CoLostruUM— Pfeiffer, . ‘ ‘ 85-75 2:38 3°39 8-60 Lajoux, Ist day, . | 83-45 3°50 4-50 8-08 0-46 » 2hdays, .| 89:30 | 145 | 5-91 3-05 TABLE CIX.—Variations IN ComposiTioN oF Human MILK Dourine Lacration. | 1 : Refrac- : tive Water. Fat. | Sugar. Proteins Ash Index | | of Fat | at 35° | Per ct. Peret.) Per et. Per cent. Per ct. : Milk that did not agree ((.@ BR.) 88-11 12-95 | 628 2360 | OBL | 54-3" Normal Milk, 4 to 6 days ,, S801 , 2-97 | G47 | 225 10-30 | 53-2° 6 » Ttol4,, ,, 88-27 3-06} 662 | 185 10-26 | 515° wo ax EG Ua. oe 87-74 | 3-42 | 6-95 | 167 O22 | 51-4° ‘ » over 30 ,, ., 88-53 | 3-00 | 6-83 1-430 0-21 | 51-7° | First Month (Pfeiffer), . [S818 274) S77) 29S G24] .. Second _,, 55 . | 88-22 | 3:37 | 6:33 | 204 , 0-18 Third 7 is | 88-00 2-71 | 643 | 1-99 0-18 | {Fourth — ,, s 87-56 }3-91 ) 689) 177 O15 ( Fifth, ,, 2 88-77 13:36) 7:33) 145 0-19 Siath 5 4 88-31 2:79) 683] 154 0-23 Seventh ,, 5 . 89-43) 3-28) 689 | 153 0-18 H Eighth _,, - . | 88-49 13-36 | 6-31 | 1-69 0-16 Ninth = a » 89-25 241] 662) 154 0-17 Tenth ae a S779 4:22 5 G24) 171 Olt ! Eleventh ,, 55 87-92 | 3:59 | 6-66 | 147 Olt eo Twelfth ,, us 86-71 | 5:30 | 6-09 | 1:73 0-16 2 4 Thirteenth ,, 3% 88:55 2-94} 6-68 | 165 0-15 eo * Leeds gives the average composition as :— Water, . 86-733 per cent. Protein, . 1-995 per cent. Fat, . . #131 ,, Ash, . . O01 ,, Sugar, . 69386 —,, His figures, however, do not agree with the average deduced from his analyses. There is internal evidence that his analyses are not so reliable as the other series, and comparatively little weight must be given to his series. He examined sixty-four samples derived from eighty women, some of his samples being the mixed milk of six women. 394 THE MILK OF MAMMALS OTHER THAN THE COW. TABLE CIX.—Continued. Water. Fat. Sugar Proteins. Ash. Per cent | Per cent, | Per cent. | Per cent. | Per cent. lst to 11th day (Leeds), 86-49 4:28 2-32 0-23 11th to 3lst ,, 35 86-60 3-90 7-06 2-01 0-20 3lst to 91st ,, *% 86-99 3-97 6-99 1-80 0-21 Over 91 days, 86-51 4-44 7-09 1-76 0-22 at 4 to 10 days (Lajoux), 85-13 5:49 6-12 2-95 0-32 8,, ll ,, (Camerer & Séldner), | 87-99 2-92 6-39 2-38 0-27 20,, 40 ,, Ist series, 87-54 4-04 6-36 1-79 0-22 70,, 120 ,, n 88°33 3-29 6-66 1-49 0-18 17) or over, 5 | 89-35 2:47 6-87 1-07 0-18 lto 3 days (Camerer & Soldner), | 87-35 2-92 4-96 3-25 0-41 5,, 6 ,, 2ndseries,* | 87-93 3-26 5:83 1-83 0-30 8x5. 12: - 5, : : 87-88 3-11 6-16 1-72 0:28 20,, 40 ,, 87:52 3-91 6-52 1-30 0-22 60,, 120 ,, : 88-21 3°31 6-81 1:10 0-19 170 or over, 5 88-56 3-20 6-78 0:95 0-18 Variation with Lactation.—There exist several series of analyses in which the time which has elapsed since parturition has been noted. Of these, the results of Carter and the author represent normal milks, those which disagreed with the child in any way having been excluded. The Tables due to Pfeiffer, Leeds, and Camerer and Séldner contain all the analyses made by them without any eliminations (Table CIX.). Probable Mean Composition.—From the above results the following probable composition may be deduced for normal human milk after lactation has become regular :— Water, . ‘ . ‘ é . 88-2 per cent. Fat, . ‘ < ‘ : ‘ » B38 ys Sugar, 2 : : F r 6-8 59 Protein, ; i i ‘ ‘ 15 ies Ash, . : : : . - 02 Variation of Constituents.—The following maxima and minima have been found :— Per cent. Per cent. Fat, . : . 9-05 (Pfeiffer), 0-47 (C. and R.). Sugar, ‘ . 889(C. and R.), 4-22 (Pfeiffer). Protein, F . 5:56 (Pfeiffer), 0-85 (Leeds). Ash, 0-50 (C. and R.), 0-09 (Pfeiffer). *In Camerer and Séldner’s second series the proteins are obtained by multiplying the nitrogen by 6-38. HUMAN MILK. 395 Composition Before and After Suckling.—The average composition of 37 samples taken before and 37 samples after suckling was found by Carter and the author to be— TABLE CX. Hl 1 Befure Suckling. | After Suckling. Per cent. Per cent. Water, « . . ‘ 88°33 88 04 Fat, . . . . ‘ 2°89 3:18 Sugar, . . ° 6°51 653 Protein, . . . , 1:99 1:99 Ash, . . . 0°28 0-26 In one case, where the secretion was excessive, the analyses before and after suckling were practically identical; in another, where a very deficient supply was given, the fat differed greatly. TABLE CXI. Excessive Secretion. Deficient Secretion. Before After ~~ Before After Suckling. { Suckling. | Suckling. | Suckling. ‘ Per cent, Per cent. Per cent, Per cent. Water, . . . . 87°40 $7°36 90°59" 87°65 Fat, x . . ‘ 3°12 Bi bes 0-98 407 Sugar, . : : 3 668 6-70 6°52 631 Protein, ote : 2-49 2°51 171 177 Ash, ‘ ‘i P é 0-31 0°31 0:20 0°20 In 15 cases the fat was higher before suckling than after suckling, and in 21 it was lower, while in 1 case it was identical. The cases in which the fat was higher before suckling than after were generally when the mother was lying down, indicating that the separation of cream was largely mechanical. Analysis of Human Milk.—As the quantity of the sample is often very limited, the Gerber-Ritthausen method for the analysis of human milk is useful; 5 c.c. are diluted with 100 c.c. of water, 3 c.c. of copper sulphate solution added. and caustic soda solution drop by drop till the precipitate settles readily ; the precipitate is collected in a Gooch crucible washed with water, and dried in the water-oven. The fat is extracted by percolating with ether, and the crucible after several percolations being allowed to stand in a beaker containing ether overnight. The ether is evaporated and the fat weighed, and if very dark 396 THE MILK OF MAMMALS OTHER THAN THE COW. green in colour, the fat should be extracted with dilute hydro- chloric acid, and the amount of copper estimated and subtracted from the weight. The refractive index of the fat may be deter- mined. The Gooch crucible is dried to constant weight, and ignited ; the difference between the two weights gives the pro- teins. The milk-sugar may be estimated in the filtrate by Fehling’s method. - The author has found that the aldehyde figure multiplied by 0'134 gives a close approximation to the proteins. Comparison with Cow’s Milk,—The following differences in composition of the various constituents from that of the cow have been noticed :— Fat.—This is very low in volatile acids (see p. 391). It appears to contain free fatty acids; Leeds noted that many of the fats extracted from the copper-protein precipitate obtained by Ritthausen’s process were tinted green; Carter and the author confirmed this, and found the following percentages of copper oxide (CuO) in the fats thus extracted :— 2°80 1:27 0°87 0°62 0 30 The copper could be easily removed by shaking with dilute hydrochloric acid, and the fat behaved to copper salts in every way as if it contained free fatty acids. Carter and the author found the refractive index at 35° C. to vary from 58°4° (in a milk which upset the child, which finally died in convulsions) to 48°2° (in a milk on which the child throve remarkably well). The analyses of these two samples were :— TABLE CXII. Water Fat. Sugar. Proteins. Ash. Refractive Index. Per cent. Per cent. Per cent. Per cent Per cent. 89:54 0-87 5-19 4-02 0°38 58-4° 87:10 3-95 Tl 1-64 0-20 48-2° Sugar.—Carter and the author found that the sugar crystal- lised in rhomboid plates (not the wedge-shaped crystals of milk- sugar), and had a specific rotatory power of [«], = 48°7°. The sugar was estimated by difference in the milk, as it was found that polarisation and estimation by Fehling’s solution did not give satisfactory results. It was found that the gravi- metric results were from 0°56 to 0°98 per cent. below the difference, and averaged 0°71 per cent. below, while the polarimetric results HUMAN MILK. 397 were from 0°85 to 2°22 per cent. below the difference, and averaged 1°30 per cent. below. It was noted that by precipitating the sugar crystallised from water with dilute alcohol an amorphous substance separated, soluble in water. The [«]» of the organic solids of the mother liquor from which the sugar was crystallised was 26°8°. These facts seem to indicate that more than one sugar was present. Proteins.—The proteins differ from those of cow’s milk by not giving a curd with rennet, and by giving a much finer precipi- tate with acids. By the addition of calcium phosphate they can be made to approach much more nearly in behaviour to those of cow’s milk. The proteins of human milk are not precipitated by copper sulphate from a solution neutral to phenolphthalein, but require a further addition of alkali; the precipitate thus obtained yields a black ash, while the proteins of cow’s milk precipitated from a neutral solution leave a green ash. Mineral Matter—Harrington and Kinnicutt give the fol- lowing mean composition of the ash :— TABLE CXIII. Per cent. Uncombined carbon, si ‘ 0-71 Chlorine, Cl, . 3 4 ‘ : . 20-11 Sulphurous acid, SO,, - ‘ ‘ . . 4:38* Phosphoric acid, P,O;, . és j ‘ 10-73 Silica, SiO,, . . : Z ‘ : O70 Carbonic acid, CO., ; 5 2 2 797 Tron oxide and alumina, (FeAl),0,,_ . : 0-40 Lime, é u ‘ : x P 15-69 Magnesia, i : 2 : ‘ » AAD Potash, . ‘ , x s 3 _ 29-844 Soda, . 3 . ¢ . i P 12-397 104-85 Less oxygen = chlorine, » 453 100-31f The presence of citric acid has been established, and is about O'l per cent. Béchamp describes a starch-hydrolysing enzyme. The author has established the presence of a proteolysing enzyme analogous to that described by Babcock and Russell in cow’s milk. The Milk of the Buffalo.—This has been examined in Europe by F. Strohmer, W. Fleischmann, A. Pizzi, and D Alzac. * Given in original as sulphur, 2-19. + Given in original as potassium, 24:77 ; sodium, 9-19; oxygen, 6-16. {¢ The total is given in original as 100-54. 398 THE MILK OF MAMMALS OTHER THAN THE COW. Composition —They give the composition as— TABLE CXIV. ! 1 Strohmer. oe Pizzi. | D'Alzac. Specific gravity, . 3 1:0319 | 1-0339 | 1-0332 | Water, . : . percent. | 81-67 | 82-93 | 82-20 | 82:05 Fat, : - ; 53 9-02 7:46 7-95 7:98 Proteins, . . 6 3-99 4:59 4-13 } 5-18 Milk-sugar, . - 5 4:50 4:21 4:75 | 4:00 a a ne ie 0-77 | 0-81 | 0-97 | 0-79 Strohmer draws attention to the high percentage of fat and the musk-like smell. It is white in colour, and the butter pre- pared from it has only a slight yellowish tinge. Fat.—The analytical figures for the butter fat are given by Strohmer as— Melting Solidifying Solidifying point Potash Reichert-Wollny point point. of fatty acids absorbed. figure. 31-3° 19-8° 37-9° 222-4 milligrammes. 30-4 c.c. and by Pizzi as melting point, 38°0°; solidifying point, 290°; Reichert-Wollny figure, 26'2. Milk of the Gamoose— Composition.—The composition of the milk of the Egyptian gamoose or water-buffalo, which is the same as, or very closely allied to, that found in India, South Africa, Hungary, and Southern Europe, has been studied by the author and A. Pappel. The average composition is— TABLE CXV. Specific gravity, - 10354 Water, ‘ : . 84-10 per cent. Fat, F : - 556 4, Sugar, : - 5Al 35 Casein, ‘ ‘i - 3:26 » containing nitrogen, 0-511 Albumin, . _ - 060 ,, 5 ss 0-094 Ss . 3 ay ” ash, 0-85 alte, 2 Oe Ag ” citric acid, 0-30 Nitrogenous bases, . 0:09 % » nitrogen, 0-035 A rise in specific gravity on standing was noticed, amounting to, in 6 hours, : : 7 - + 00006 24 hours, . . . . + 0:0007 ‘One sample, however, showed a decrease. THE MILK OF THE BUFFALO. 399 The fat was found to vary from 7°35 to 5°15 per cent., and the solids not fat from 10°67 to 10-07 per cent. The average percentage composition of the solids not fat was— Sugar, 3 : 3 - : : . 49-5 per cent. Protein, . ‘ 3 : : » 408 ,, Ash, z : 5 3 2 2 ¢ 82 4, Other substances. “ , , é » 15 ” Showing a ratio of sugar : proteins: ash = 6:5:1,. The following formula was found to be applicable to gamoose milk :—T = o27 4 +1191 F., indicating that the fat had a density of 0°934, and the solids not fat had a density of 1°589, The formula + = — 0-761 F + 4L + 25714 P + 8-46 A (see p. 73) was found to be applicable to the milk of the gamoose. Two series of investigations into the constituents of the milk were made, one during the winter on milk yielded by a newly- calved gamoose, and the other during the summer on the milk of animals well on in their period of lactation. Notable differ- ences were found. Fat.—The fat gave the following figures on analysis :— TABLE CXVI. | Summer Winter. Potash absorption, . milligrammes 231°7 2204 Insoluble fatty acids, is 86-9 S75 Mean combining weight, . ; : 265-0 270°5 Iodine absorption, . . per cent. 35:1 418 Soluble fatty acids, . F " 6:99 6:09 (calc. as butyric), | Reichert-Wollny figure, . ¢ Ges 34°7 254 Iodine absorption of fat, . per cent. | 32°0 35°0 A winter sample of fat was found to contain 0°05 per cent. of sulphur and 0°01 per cent. of phosphorus. J. N. Dutt finds the average Reichert-Wollny figure of buffalo “chee” in India 34°5 e.c., with a mininum of 30 c.c. ; the oleo- refractometer figure is — 32° to — 35°, and the melting point 35° to 36°C. Casein.—The casein was prepared from the winter milk. The purest preparation contained 2°53 per cent. of moisture and 0°60 400 THE MILK OF MAMMALS OTHER THAN THE COW. per cent. ash, the nitrogen calculated to the pure substance being 14°66 per cent. and the phosphorus 0°85 per cent. Other pre- parations, which were less pure, gave about 14°4 to 145 per cent. of nitrogen. Though this casein was precipitated three times, and thor- oughly washed with water each time, and finally with alcohol and ether, it was perhaps not pure, as a solution was made in a mini- " mum of caustic soda, and equivalent amounts of sodium phos- phate and calcium chloride added, and the nitrogen was estimated in this and in the precipitates obtained by (1) saturation with magnesium sulphate, (2) tannin, and (3) acetic acid at 40° C. Calling the nitrogen in solution 100, the following amounts were obtained by Magnesium sulphate, F : ‘i ‘ « 95-2 Tannin, 3 ‘ ‘ é ‘i . » 96°6 Acetic acid, . : F 2 3 : ~ 94-7 Albumin.—The albumin contained 15°75 per cent. of nitrogen, and is probably identical with that of cow’s milk. Citric acid was identified by isolating it and determining the percentage of calcium in the calcium salt. A yellow crystalline mercury compound was isolated from the winter milk in too small a quantity for identification, but was in all probability derived from a nitrogenous basic substance. Sugar.—The sugar was prepared from the winter milk. Two preparations gave the following figures :— Influence on [a] Cupric reducing Water of density. Db, power, crystallisation. 3°94 48-66 73-6 4:77 3-94 49-10 73-9 4:82 Mucic acid was not obtained by oxidation with nitric acid. On treatment with acid the following figures were obtained :— le], Cuprie reducing power. 53-74 101-0 figures approaching those given by dextrose. This sugar evidently differed from milk-sugar, and was named “ Tewfikose.”’ A second preparation was made from the summer milk; it was examined by A. R. Ling and the author, and yielded the following figures. (For the sake of comparison figures yielded by milk-sugar, prepared by the same method, are given.) THE MILK OF THE GAMOOSE. 401 TABLE CXVII. i Gamoose Sugar. Milk-Sugar. | _— [2],» 553° 551? Cupric reducing power, . i 797 795 Influence on density, Pa 3°92 3:92 Melting point, : m4 , . | 213° to 215° | 214? tu 2207 Water of crystallisation, . percent. 5:03 5:00 (cale.) Molecular weight (from freezing point), | 341°7 342 (calc.) Carbon, . ‘ E . » per cent. 39°75 39°60 Hydrogen, : : F 2 O47 6°63 Mucic acid by oxidation with nitric acid, . F Z os ; 32 { 32 By heating with phenylhydrazine acetate two compounds were formed—one readily soluble in hot water (melting point, 197°), and the second almost insoluble in hot water, but soluble in hot dilute alcohol (melting point, 218° to 219°). These compounds agree with phenvllactosazone and its anhydride. The acetyl derivative prepared by heating with acetic anhy- dride and anhydrous sodium acetate. and crystallising from alcohol melted at 75° to 80°. When crystallised from a mixture of 90 per cent. alcohol and chloroform it melted at 88° to 95° The solution in chloroform was nearly optically inactive: if anything, slightly leevo-rotatory. A determination of acetic acid in the acetyl derivative cave 7146 per cent. as against 70°79 calculated for an octacetyl derivative. The properties of the acetyl derivative agree exactly with octacetyllactose. The birotation ratio was found to be 1°6. All the properties without exception agree with those of ordinary milk-sugar. It appears that the sugar of the summer milk is “ lactose ”’ and not “ tewfikose.” Winter and Summer Milk.—There appears to be a distinct difference between the winter and summer milks, which may be summarised as follows :— Winter. Summer. Fat low in volatile acids. Fat high in volatile acids. Contains “ tewfikose.”” Contains “ lactose.” The author has tried to find evidence that the sugar called “ tewfikose ’’ was a product of the action of reagents used in the preparation of milk-sugar, but has been unable to do so, many preparations of milk-sugar having been made by the same method (including that from summer milk), always with the properties a 402 of milk-sugar. Analyses of the milk used to prepare “ tewfikose ” THE MILK OF MAMMALS OTHER THAN THE COW. 2 only added up to 99°3 per cent., when the polarisations were cal- culated as milk-sugar, but gave a satisfactory approach to 100 when calculated as tewfikose. se There appears to be no reason to reject the view that “ tew- fikose ’’ is a separate entity. ; aren fs 5k The Milk of the Ewe.—The following composition is given by different authorities : TABLE CXVIII.—Composition or Ewe’s MILxK. Authority. | Water. Fat. Sugar. Casein. | Albumin. Ash. | Per cent. | Per cent. Per cent. Per cent. Per cent. | Pizzi, » | 80-43 9-66 4:37 4-40 1:10 Besana, - | 7823 | 950 5-00 6-26 1-01 Vieth, . - | 81:3 6-8 4:8 6:3 0:8 Bell, + 0 152 11:3 3-6 8-8 1-1 Fleischmann, . | 83-0 53 4:6 46001 17 0-8 | (average) 9 » 75-40 11-77 3-65 647° 1-64 1-06 : Raden ! herd) Piceardi, | 82-46 6-10 3:95 556 (1-01 0-93 Hucho, . . | 83-10 6:23 4-46 5-39 0-88 Trillat and Forestier, 1902, | 80°72 T 24 5°38 5°68 0°98 1903, | 82-71 6°86 | 3°23 3°62 0-98 The composition of colostrum of ewe’s milk is given by Voelcker as— | 69-74 | 2-75 | 8-85 | 17:37 1-29 The following figures are given by Weiske and Kennepohl :— TABLE CXIX.—Composirion or Ewer’s Minx. a Non- ae Water. Fat. Sugar. | Casein. |Albumin.| Ash. Pics Per ct. | Perct. | Per ct. Per ct. er Ct Per © dhour,. . | 47-03 | 95-04 | 1-s4' | “496 | is'se | ane | ot 7 hours, 61°93 | 16-14 | 3°53 | 7-48 | 9-61 | 0-96 | O41 V9) ays 76°53 8:87 | 5:24 5:27 2-93 0°S6 0:12 2 days, . 82°79 | 5°93 | 519 | 4-28 | 0-82 | 0-87 | o-41L D4 82°93 6°19 4°37 4°54 0-92 0:95 0-10 45, 83-48 | 569 | 431 | 464 | 0-85 | 0-96 | o-10 5° 83:90 | 572) 427 | 418 | o-60 | 0-92 | 0-09 Os, 85°22 | 447) 455 | 3:83 | o-7o | ogg | ous as 81-40 | 461 | 5:09 | 4:04 | 0-86 | 0-90 | 9-07 Bo 84:26 | 4-62 | 531 | 3-97 | 0-73 | o-ss | O19 9 ss 8439 | 4°71 | 541 | 449 | 0-60 | 0-90 | O08 i THE MILK OF THE EWE, GOAT, AND MARE. 403 The specific gravity varies from 1°035 to 1:043. Besana gives the following table for correcting the specific gravity to 15° C. :— TABLE CXX. Temp. Correction. 5° to 10°, Subtract 1-25 + 0-20 (10 — t )° De gg, BAe Gs <5 ri 0-25 (15 — ¢ )° 16?,, 202, . Add : 0:30 (t — 15)° en Oe » 1d +032(¢ — 20) 26F 5° 30s 58 3-1 + 0:35 (¢ — 25)° 31°,,, 35° » £85 + 03701 — 30) The fat globules vary in size, according to Besana, from 0°0047 mm. to 0°0309 mm. This is not in accord with Pizzi’s observa- tions (p. 390), Sheep’s milk throws up no cream if left to rest, owing to its great viscosity. The cream may, however, be removed by a separator, or by dilution with an equal bulk of water. The action of rennet does not differ from that with cow’s milk, but the curd is firmer. The Milk of the Goat.—The following is the mean composition given by various authorities :-— TABLE CXXI.—Composirion or Goat's MILK. F ; i : ' Authority. Water, Fat. Sugar. Casein. | Albumin. | Ash. i | j Percet Per ct. I Per et. Peret, Let-cte [Perats K6nig (average), . S57L | $78 | 446 320 1-09 O76: | Moser & Soxhlet, . SU-48) | 4:43 | 4°56 Biro 0:30 O79 | | Fleischmann, 7 85:5 48 | 4:0 3:8 3: wi 4 | Pizzi, . 4 . 86-75 | 5:35 3-60 3-64 0-66 | Author, ‘ ‘ 80-76 | 3°78 4-49 4:10 0-87 | Piccardi, F i 82-46 | 6-10 | 3-95 | 5-36 | 101 0-93 ¥ 1 ‘ WV -. Pog Steinegger, . - | 8840 3-25 4-80 3-92 0-63 | None of the constituents differ sutticiently from those of cow’s milk to need detailed notice. The fat is, however, very white, and the milk and butter have a smell of the goat. The Milk of the Mare.—Most of our knowledge of mare’s milk is due to Vieth, who carried out an extended series of obser- vations on the stud of mares at the International Health Exhi- bition in London during 1884. 404 THE MILK OF MAMMALS OTHER THAN THE COW. The following is an abstract of his results :— TABLE CXXII.—Composition or Mare’s MILK. | Water. Fat. © Sugar. Protein. Ash. Mixed milk. Percent. Percent. Per cent. Per cent. | Per cent. Average,. . . | 90-06 1-09 6-65 1:39 | 0:31 Maximum, P ‘ 90-41 1-44, 6°82 2-11 0°34 Minimum, . . | 8974 0-87 | 630 171 , 0-29 Milk of individual mares. Average, . F 7 90-13 0-94 6-98 1-65 0-30 Maximum, ‘ 90-46 | 118 721. 1:76 0:36 Minimum, ‘ 89:88 | 0-62 6-70 1-5} 0-26 Milk of mares specially fed. Average, . z ‘ 89-22 1-48 7:03 1-99 0-28 Maximum, ‘ “ 89-88 2-14 7:28 2-20 0:32 Minimum, r » 88:24 1:18 6:67 1-70 0-24 Fleischmann gives the following composition :— Average, . 90-7 1-2 5-7 2-0 0-4 Maximum, 92-53 2-45 7:26 3-00 — 1-20 Minimum, 89-05 0-12 4:20 1:33. | 0-28 The following composition is also given :— Authority. Landowsky, Biel, ‘ ‘ Camerer and Séldner, 89-29 1-16 7:32 1:87 0:36 90-42 1:31 5-43 2°55 0-29 90-58 1-14 5:87 2-05 0-36 Vieth gives the following composition of samples of con- densed mare’s milk (containing cane-sugar 16 to 18 per cent.). I. é : a 26-73 | 4-77 53-07 13-69 1-74 a ieee ‘ 2 : 24-04 6-20 55°81 12-17 1-78 UL., 3 . 17-90 12-07 54-88 13-50 1-65 IV., , 5 18-80 10-08 54-09 15-23 1-80 Vieth describes the milk as of a chalky white colour, of sweet, and at the same time somewhat harsh taste, and of aromatic flavour. It had usually an alkaline reaction, the very few exceptions being neutral. As this milk undergoes alcoholic fermentation very easily, while cow's milk does not, there is reason to suppose that the sugar is not identical with milk-sugar. The Milk of the Ass.—The milk of the ass is considered by some authorities (e.g., Tarnier) to approximate more in com- position to human milk than that of any other animal; it is used to some extent for infant feeding. THE MILK OF THE ASS. 405 The following is the composition given by various authorities :— TABLE CXXIII. SS bs a eee — aA Gaeon vases Authority. Water. Fat. Sugar. | Casein. | Albumin. Ash. i Per cent.| Per cent. | Per vent. | Per cent. ' Per cent. Per cent. Duclaux, 90-70 1-00 G54 1 0-99 | 0-34 0-43 ae Author, . 39-77 1-18 6-36 | 174 O45 aS ee Schlossmann,. | 88:85 | 036 | 494 | os | 033 | 031 Konig (mean), 90-12 1:37 6-19 | O79 1-06 O47 Pizzi has shown that the fat is somewhat low in volatile acids (see p. 391). The author has prepared the suvar and finds that it has a specific rotatory power [¢], = 52° (for hydrated sugar), a birotation ratio of 1°6, and corresponds in every particular with milk-sugar. The milk has a very feeble alkaline reaction ; rennet produces a very soft curd after a long time, and acids sive a finely divided precipitate. On boiling, it has a tendency to curdle and deposit flakes (coagulated albumin ?). It has a white colour and a sweet taste. The aldehyde figure multiplied by 0°154 gives a close approxi- mation to the proteins. Milk as a Food and a Medicine.—In considering the food value of milk, two points must be borne in mind; first, its value in repairing the waste of the tissues; and second, its value as a source of energy. .\s a food for infants it is required not only to repair waste of tissues, but to actually build them up. Composition of Constituents—The following table gives the percentage composition of the three main coustituents of milk :— TABLE CXNNIYV. ! ; | | Carbon. Hydrogen. | Oxygen. | Nitrogen. Sis | es ——— Ss | Percent. | Percent. Per cent. Per cent. Fat, « & «, Bee Tare | aeae Sugar. 42-11 643 5 5146 ee Protein, v3 ‘ WaT 15°77 t 52-66 | It is seen that fat is the richest in carbon and hydrogen, protein next. while sugar occupies the lowest place. Neither fat nor 406 THE MILK OF MAMMALS OTHER THAN THE COW. sugar can replace proteins, as these compounds form the only source of nitrogen. Fat and sugar being composed of the same three elements may replace each other, but it is evident that in building up tissues containing high percentages of carbon and hydrogen, fat is a far more advantageous food than sugar. As a food for infants the value of milk largely depends on the fat present, and it is doubtful whether fat can be replaced by sugar without detriment to anabolic processes. ‘ As a food for adults, where the tissues are ready formed, milk may be regarded chiefly as a source of energy. From this point of view fat may be replaced by the iso-dynamic quantity of milk- sugar. Heat of Combustion of Constituents.—The following values for the heat of combustion of the constituents of milk are due to Strohmer :— TABLE CXXY. Fats—Butter fat, . 9231-3 calories per gramme. Other fats, ‘ « 9600 Ze 95 Sugar—Milk-sugar, . . 3,950 i sh Cane-sugar, . 38,955 i Proteins—Casein, . ‘ 5,858°3 3 4s Albumin, : = 6,735°2 39 % These values assume that complete combustion takes place, and that carbon dioxide, water, and nitrogen are produced. In the case of fat and sugar it may be fairly assumed that an approach to complete combustion takes place in the human body, and that carbon dioxide and water are excreted. The nitrogen of proteins is not excreted as nitrogen, but as com- pounds, of which urea may be taken as the type. Strohmer calculates that 1 gramme of average protein yields 0°3428 gramme of urea, the heat of combustion of which is 2,537 calories per gramme; the heat of combustion of the urea from 1 gramme of proteins is, therefore, 869°7 calories, or, in round figures, 15 per cent. of the total heat of combustion. It is necessary, therefore, to deduct 15 per cent. of the heat of combustion of proteins im calculating iso-dynamic metabolic ratios. In round figures, the following will be the calories per gramme developed in combustion of the three constituents in the human body :— Calories. Fat, - 9,230 Sugar, ‘ . . 8,950 Proteins, : é . 4,970 These figures are in the ratio of 2°38: 1: 1-26. MILK AS A FOOD. 407 The author proposes to calculate the ratio between the various constituents as follows :— Anabolic ratio = fat: sugar: proteins. Metiholiecatia: = fat < 2-38 + sugar oe proteins x 1:26 proteins Instead of the figures 2°38 and 1:26, the round figures 2°5 and 1°25 may be used without appreciable error. The author believes that the above ratios will give a truer idea of the proportionate value of different constituents than the usual nutritive ratio, fat x 2°5 + sugar protein : Food Value.—We may now consider the food value of various milks. The ratios for human milk are Anabolic ratio, 22:4:3:1 Metabolic ratio, 11:3 which is For cow’s milk— Anabolic ratio, ‘ 115 Metabolic ratio, TAY | The marked difference of the two milks, due to the smaller amount of proteins in human milk, is very apparent. It is assumed in calculating these ratios that the constituents are all digestible; this is approximately true with human milk. The same cannot be said of cow’s milk, owing to a difference in the proteins; the action of rennet, one of the enzymes of the stomach, on cow's milk results in the formation of clots of curd, which are not readily digested. If the fat has been partially churned in the milk, this also is not perfectly digested. Experiments have shown that children do not derive the most benefit from milk unless the anabolic ratio approximates to 2:4:1, and the constituents are in such a form that they are as finely divided as possible in the stomach. Milk as a Food for Infants—Artificial Human Milk.—Many preparations of artificial human milk, or humanised milk, are made; they correspond in composition more or less exactly with human milk. The condition of the proteims necessary to produce a fine state of division in the stomach is attained— (1) By simple dilution with water, and addition of fat and sugar. (2) By removal of casein, and addition of fat and sugar. — (3) By acting on the milk with a proteolytic enzyme—.e., peptonising it, and addition of tat and sugar. (4) By adding a preparation containing diastase and diluting it, and adding fat and sugar. : (5) The fine division of the proteins is aided by the presence of a colloid, such as the small proportion of starch in barley water. 408 THE MILK OF MAMMALS OTHER THAN THE COW. Various sugars are used, milk-sugar naturally being the most universally adopted; while cane-sugar, and maltose, and other carbohydrates, resulting from the diastatic conversion of starch are added. 2 The artificial feeding of children is to a large extent empirical. There is strong reason to believe that few of the constituents of cow’s milk are identical with those of human milk, though closely analogous; yet it has been found that cow’s milk suitably modified is an excellent food. ; Again, it is found that human milk decreases in proteins as lactation advances. The best results have been obtained in artificial feeding by an exact reversal of this rule. Peptonised Milk.—It is now conceded by the best authori- ties that the use of peptonised preparations is not an advantage, as, though the digestibility of the proteins is increased, it is at the expense of the development of the digestive organs. The value of the milk in the treatment of disease lies in the fact that it is readily digestible, especially if diluted or modified so that the formation of hard curd in the stomach is prevented. As an example, it may be mentioned, that during the epidemic of typhoid at Maidstone in 1897, the Aylesbury Dairy Company sent many hundreds of bottles of humanised milk to the hospitals, which gave most satisfactory results, and provided a food which was readily retained and assimilated. Peptonised milk is also used in cases of gastric disorders. Vieth gives the composition of this product as :— TABLE CXXVI. Water, ‘ 3 . $920 per cent. Fat, , : P 3 . $41 4 Sugar, 4 ‘ é 3°80 4 Casein, : : 4 : 0-96 a Albumin, . . ‘ - 0:07 am Albumoses, ‘ ‘ ‘ . 1:88 3 Ash, . u F F ‘ ‘ 0-68 is Diabetic Milk.—In cases of diabetes, Ringer has recom- mended a solution of casein in a mixture of salts approximating to those present in milk as supplying protein nourishment; and Overend has used a diabetic milk in which the milk-sugar has been almost entirely replaced by levulose with success. The author found diabetic milk to have the following com- position :— MILK AS A MEDICINE. 409 TABLE CXXVII. Water, i F - 90°50 per cent. Fat, . . Z : . - 2-48 : Levulose, . 2 : ‘ F a Gal, ox, Milk-sugar, . : : F ‘ %- “OME | 5. Protein, é : A ‘i » Wt yy Ash, . é : 2 ¥ F O45 Koumiss is a remedial agent of great use in gastric disorders and many other diseases (see p. 297). It owes its value to the fact that it is, first, a food of great digestibility ; and, secondly, owing to the presence of alcohol, a stimulant. It is retained in cases where absolutely no other food can be given. 410 CHAPTER IX. STANDARDISATION AND CALIBRATION OF APPARATUS. I. Weights.—A good set of weights is a sine qué non in a laboratory ; they should consist of the following :— 100, 50, 20, 10, 10, 5, 2, 1, 1, 1, grammes, and 05, 02, O11, O11, 0°05, 0°02, 0°01, 0-01 gramme, and some riders each 0'01 gramme. Select one of the weights, preferably a 10 gramme, as a standard; mark one of the 10 grammes and one of the 1 gramme with a mark (’) by means of a fine steel point; mark another 1 gramme with a mark ("); turn up one corner of a 0'l gramme and of a 0-01 gramme. By this means the weights can all be distinguished from each other. See that the balance is in adjustment by swinging it without any weights in the pans; if the pointer does not travel to an equal distance on both sides, alter the adjustment till this end is attained. After the adjustment, leave the balance for at least one hour and see if it is still in udjustment ; if not, repeat the process, handling the beam, &c., as little as possible. When the balance is in proper adjustment, place the 10-gramme weight on the right-hand pan, and the 10’-gramme weight on the left-hand pan; they should very nearly balance, and the pointer should swing nearly equally on both sides; if they do not balance, place the rider so that the balance is restored. The value of the 10’-gramme weight can now be obtained in terms of the 10-gramme weight, by adding the readings of the rider, if on the right arm, and subtracting, if on the left arm. Now reverse the weights, placing the 10-gramme weight on the left-hand pan, and the 10’-gramme weight on the right-hand pan, and repeat the weighing; the value of the 10’-gramme weight can be obtained in terms of the 10-gramme weight by adding the readings of the rider, if on the left arm, and subtracting, if on the right arm. Owing to minute differences in the lengths of the arms it is not unusual to find a difference between the two: values, The true value may be found by adding the two values together and dividing by 2. (It is more correct, theoretically, to multiply the two values and take the square root, but the values thus obtained are practi- cally identical with the arithmetical mean.) The total value of the 5+ 2+ 1+ 1'+ 1” weights are similarly obtained. The value of the 20-gramme weight is obtained in a similar manner by weighing it against the 10+ 10’, 10+54+2+1+4+1'+1", or the 10°+542 +1+1'+1" or, preferably, by weighing against all three series and taking the mean of the three values (which should not differ appreciably). The value of the 50-gramme weight is obtained by weighing it against the 20+ 10+ 10'+54+24+1+1'+1" weights. The value of the 100-gramme weight is obtained by weighing it against the 50 + 204+ 104+10'+54+2+1+4+1' +1" weights. The 5-gramme weight is now taken, temporarily, as a standard, and the 2+1+1'+1" weights are weighed against that, and the value of the series obtained in terms of the 5-gramme weight. VALUES OF WEIGHTS. 411 The true value of the 5-gramme weight is obtained by the following formula :— Let 10+ 2 be the value of the series 5+2+1+1'4+1’, 5 xa+y, the value of the series 2+ 1+ 1 +1’ in terms of the 5-gramme weight, and 5 x a@ the true value of the 5-gramme weizht ; then lW+e=2(5xa)ty, ‘ie sae 2? Now, temporarily assume that the l-gramme weight is the standard, and ascertain the values of the 1’ and 1” weights; then ascertain the value of the 2-gramme weight by weighing it against 1+ 1’, 1+ 1” or 1’ +1’ or, preferably, against all three. The apparent values of the 2, 1, 1’, and 1” weights in terms of the l-gramme weight will now he obtained. The true values are obtained as follows :— Let 1x b be the true value of the l-gramme weight, and 2.x b)+2, lLxb+u,lxb+u, the values of the 2, 1’, and 1” in terms of the l-gramme weight ; then 2&lLxb)+z4+1 xb+lxbeuw+ l xbtn =5xaty, ob xaty- town or Teh 5 From the true value of the I-gramme weight, the true values of the 2. UV. and 1” weights ave obtained. fhe values of the fractions of a gramme are obtained by the same process as the values of the 5, 2, 1, 1’, and 1” weights. TABLE CXXVII.—VanLves or Wercuts. Weight. True Valne Correction. 100 100-0031 +0:003 1 50 5O-OU2S +0028, 20 19-9992 — 00008 10 10-0000 fee 10’ 9-499] = O-0009 5 50002 +0-0002 2 2 0007 + U-O007 1 O 9989 -O0-0011 Vv 0°9993 — W-G007 a 10001 + 0-0001 0-5 04997 -— 0:0003 Oz 02002 +0-0002 Ol 0 1601 +0-0001 O01’ 0:0998 — O-UU2 0:05 0:0497 — 0°0003 0-02 0-0200 = 0000 0-01 U-0097 =~ 00035 ool 0-099 = O00] Rider 00101 +0-0001 412 STANDARDISATION AND CALIBRATION OF APPARATUS. It is best to weigh the series 0°5, 0:2, 0°1, 0'l’, 0:05, 0:02, 0-01, and 0-01’ against the 1, 1’, and 1” weights, and take the mean of the three values so obtained. When the weights have been standardised, a table should be drawn up in the above fashion (Table CXXVIIL.). . : : II. Burettes.—Carefully clean out the burette with hot chromic acid mixture and rinse well with distilled water. Place it in a situation where sudden changes of temperature can be avoided, and fill it above the zero mark with distilled water ; note the temperature of this, which should he as near as possible 60° F. (15°5° C.). : : Weigh an empty weighing bottle provided with a stopper; cut two parallel slits about 2 inches long and three-eighths of an inch apart ina card (a visiting card answers admirably), and bend this so that the burette passes through the slits, the narrow strip being in front; adjust this so that the upper edge of the narrow strip is coincident with the graduation next below the zero mark. Now carefully run out the water so that the lower edge of the meniscus coincides with the zero mark, cork up the burette and leave it for a few minutes; after making sure that no alteration in level has occurred, adjust the card to the graduation next below the 5 c.c. mark, and run out slowly 5 c.c. into the weighing bottle. Weigh this and subtract the weight of the empty bottle ; the difference will give the weight of water occupying the volume between 0 and 5. After making sure that the level has not changed, adjust the card to the graduation next below the 10 c.c. mark and run out a further 5 c.c. into the weighing bottle ; weigh again, and subtract the weight of the empty weighing bottle ; the difference will give the weight of the water occupying the volume between 0 and 10. Repeat this process till the lowest mark on the burette is reached. The calibration of the burette should be repeated two or three times and the mean values tabulated. With a finely-divided rule measure the lengths of the divisions 0 to 5, 0 to 10, &c. ; multiply each of these lengths ty the total weight of water and divide by the total length, to obtain figures commensurate with the weights of water. Now plot out on squared paper two curves, one taking the scale readings as ordinates, and differences between scale readings and weights of water as abscissze; the other taking scale readings as ordinates, and differences between scale readings and lengths of scale corrected as described above as abscissa. Tf both curves are nearly straight, it shows that the burette is made from a tube of uniform bore, and is correctly divided ; if the two curves have a marked curvature, but coincide in form, it shows that the burette is made from a tube of uniform bore, but incorrectly divided ; if the two curves do not coincide it shows that the tube is not uniform in bore. Now, obtain the value of the weights of water contained in each 5 C.G., 0 to 5,5 to 10, &e., by subtracting the weight contained in 0 to 5 from that contained in 0 to 10, &c., and the value of the lengths in a similar manner ; divide one value by the other and plot out the values so obtained on squared paper, taking the mean scale readings (i.e., for the volume 0 to 5 take 2°5) as ordinates, and the values obtained by the division as abscisse. This will give the curve of irregularity of bore; if at any part of the curve it is noticed that the irregularity is very gross, the volume of cach 1 ¢.¢, should be obtained by weighing the water ; if the curve is appreciably regular, it is evident that the errors of the burette must be due to incorrect division, and very careful measurements of the lengths of divisions intermediate between cach 5 c.c. mark should be made; and if any very yrave faults are found, the burette should be especially calibrated at that point. It is better, however, not to use a burette of this description. Table CXNIX will give the figures obtained on a burette of fairly even bore, but badly divided. PIPETTES, FLASKS, GERBER BOTTLES. 413 TABLE CXXIX.—Catipration oF BcRETTE. Weights of 5 i z Scale. Water Difference. dnote. conn 0 to 5 4°918 — 0:082 1752 — 0-022 0 to 10 9-940 —0°060 3°550 +0°016 0 to 15 14°912 — 0-088 5:329 +0°001 0 to 20 19896 — 0-104 7-1095 -0°010 0 to 25 24°$80 -0°120 8-890 - 0-023 0 to 30 29°908 — 0:092 10°683 +0°000 0 to 35 34°849 -0°151 12-436 —0:087 0 to 40 39°817 - 0°183 14-204 —0:135 0 to 45 44-817 -— 0183 16-982 —0°153 0 to 50 49°877 - 0123 17-7775 ~-124 III. Pipettes.—Pipettes are used for measuring liquids by filling them to the mark and letting the liquid run out; the following points should be noticed :— (a) The bottom of the meniscus should coincide with the mark. (b) The pipette should be held vertically while it is running out. (c) The liquid should always be allowed to run out in the same manner. Perhaps the best manner of allowing the liquid to run out is to allow it to flow as fast as possible, and, when empty, to touch the surface of the liquid with the point and to withdraw it at once. It may, however, be allowed to run out slowly, or a definite number of drops may be permitted to run out after the main portion is delivered. Whatever method 1s. adopted during graduation must be strictly adhered to in practice. The graduation of pipettes is very simple; they are tilled with water as near 60° F. (15°5° C.) as possible, the contents run into a weighing bottle and the water weighed. The pipettes should be each etched with a number and the weight of water delivered tabulated for use. Pipettes used exclusively for delivering known weights of milk should be graduated with milk of 1:032 specitic gravity containing from 3-5 to 4:0 per cent. fat. In this case, the reading should be from the top of the meniscus, as the lower edge is invisible, IV. Flasks.—Flasks of capacity sufficiently small to permit of being weighed when full, are filled with water as near 60° F. as possible, and weighed. Each should be marked with a number, and the weight of water contained by each tabulated. Larger flasks (¢.y., litre flasks), if no balance sufficiently large is available, are graduated by the following method :—10 successive portions of a little less than 100 grammes of water at about 60° F. (15°5° C.) are weizhed into the flask (best from a 100 c.c. flask). A beaker containing a little water, and a pipette are now weighed, and the litre flask filled to the mark by water from the pipette; the beaker, pipette, and remaining water are now weighed ; the difference between the weights and the total weight of the ten portions added together will give the weight of water in the litre flask. V. Leffmann-Beam or Gerber Bottles.—These can be graduated with sufficient accuracy by using each to make determinations of fat in several samples of milk, in which the fat has been carefully estimated hy a good gravimetric method (e.g., the Adams method). Those bottles which show a marked difference (i.e., more than 0°1 per cent.) should be rejected. The scale should also be measured with a finely-divided rule, and any bottles showing marked irregularities of graduation must be likewise rejected. 414 STANDARDISATION AND CALIBRATION OF APPARATUS. VI. Lactometers.—Lactometers are graduated by taking the specific gravity of several samples of milk which have had the density determined by a pycnometer ; the range of specific gravities should be fairly wide ; no lactometer showing differences of more than 0:0002 (0'2°) should be used, unless the differences are constant, when a constant correction may be applied. PVII. Thermometers. —One thermometer should be specially calibrated, and this will then serve as a standard of comparison for others. The calibration is divided into two partr. (a) Calibration of scale. (b) Determination of fixed points. (a) Calibration of Scale.—By means of a finely-divided rule the distances between the marks on the scale (¢.g., 0 to 10, 10 to 20, &e. ; or 0 to 5, 5 to 10, &c.) are measured and tabulated. The mercury is allowed to flow into the stem, and at a point, which should be as nearly as possible 10° from the end, the tip of a fine flame is carefully applied; by a gentle jerk a thread about 10° in length can be separated from the main portion, which is now allowed to flow back into the bulb. By gently tapping the tube, the thread is brought so that one end coincides with the zero mark, and the length of the thread is carefully measured ; the thread is next brought to the 10° mark, and its length carefully measured again ; and so on throughout the whole scale. By dividing the lengths of the thread when it is between each pair of points (0 to 10, 10 to 20, &c.) by the distance between the same pair of points, the length of the thread in apparent degrees will be obtained ; the average of these lengths will give the mean length of thread in mean degrees. By dividing the length of thread between each pair of points by the mean length, the value of a degree between each pair of points in terms of a mean degree will be obtained ; and, on multiplying by ten, the distance between each pair of points in mean degrees will be obtained. The values in mean degrees of the scale from 0 to 10, 0 to 20, &c., should now be calculated, and also the lengths of scale between the same points. A curve of conicality can be plotted for the thermometer in the same way that a similar curve was plotted for a burette (q. v-.). (b) Determination of fixed Points. —A flask with a long neck is partially filled with water and placed over a flame; a shallow cork, with two holes, is fitted to the neck, and through one of the holes the thermometer is passed ; in the other a short bent tube to take the steam away from the operator is placed. The water is boiled briskly, and the thermometer pushed in till only the top of the mercury is visible, and left in this position for several minutes. The exact point on the scale where the top of the mercury rests is now noted; the atmospheric pressure is read, and, from the table below, the boiliny point of water is taken ; the difference between this and 100° (or 212° if a Fahrenheit thermometer is used) is now added to (or subtracted from) the scale reading of the thermometer, and the value thus obtained noted as the true value of 100°C. (or 212° F.). The thermometer is now removed, allowed to cool, and placed in melting ice; when the mercury is stationary, the position of the top of the mercury is noted as the freeztny point. , The difference between the observed boiling and freezing points is taken, divided by 100 (or 180 if a Fahrenheit thermometer is used); the values in mean degrees of the scale from 0 to 10, 10 to 20, &c., are multiplied by the value thus obtained, and the corrected value tabulated. The differences between these and the nominal values of the scale are now plotted on squared paper, and will serve as a curve of correction of the instrument. It is advisable to redetermine the boiling and freezing points from time to time, as they are liable to slight alteration. Other thermometers may be standardised by comparison with this one. 415 APPENDIX. USEFUL TABLES, TABLE CXXX.—Boiine Point or WATER UNDER DIFFERENT PRESSURES (due to Regnauit). Boiling Point. ae Boiling Point. Centigrade. Centigrade. . 98°5° 72015 99 -5° 98 °6° 722°75 996° 98°7° 72535 99°7° 98°8° 727°96 99°8° 98°9° 730°58 99-9° 990° 733°21 100-0° 991° 735°85 100°1° 99:2° 738 °50 100°2° 99 °3° 741-16 100°3° 99°4° 74383 100°4° Pressure in Millimetres of Mercury. 746°50 749-18 APPENDIX. 416 SPST | O8-ET | OG-ET | OL-8T | G6-GT | G8-G1 | OL: | 09-BE | O9-GI | GE-BE |] sal | OT-3T | 00-ZT | O6-IT | GL-T1 GPE OF-ET | O-ET | GOEL | S6-GT | C8-T | OLZI | O9-GI | CHI | GE-ZI | S-BE |] OL-GI | 00-2T | G8-T1 | GL-T | G9-IT O-FE OB-ET | CO-ET | 6-31 | GS-31 | OL-ZL | O9-G1 | Gh-SI | CE-BI | G&S | OT-GL |} OO-ST | CS-IT | GL-TL | $9-1T | OS-IT G-€E GO-€T | $6-GT | $8-GL | OL-GL | 09-61 | SF-aI | C€-GI | G3-ZI | O-GT | 00-2T |] SS-IT | GL-11 | ¢9-T1 | OG-TT | OF-IT 0.€€ S6-ZT | OS-ZT | OL-GT | 09-GI | SF-CT | S8-3I | OB-BI | OT-GT | 00-31 | G8-TT |] SLIT | 09-11 | OG-TT | OF IT | S@-IT G.3E 08-GE | OL-GI | 09-BT | SF-ST | SEZ | 0B-GI | OL-ZT | 00-GI | GS-11 | GL-IT |] 09-TT | OG-IL | OF IT | G3-TT | ST-TI 0-6E OL-GE | 09-B1 | SFL | SE-GT | OG-ZT | OT-GI | 00-BT | G8-IT | 4-11 | O9-TT |] OG-IT | OF-IT | GIT | GT-IT | 00-11 G.TE 09-61 | SF-GL | $E-BT | 06-GI | OL-ZT | 00-31 | G8-TT | GL-TT | O9-TL | OG-IT |] OF-IT } GG-11 | ST-IT | 00-1T | 06-0T O-TE GU-GL | CE-GL | 0G-GT | OL-GI | $6-TI | G8-TT | SL-11 | O9-TT | OG-1T | GSI |] SZ-TT | ST-1T | 00-11 | 06-01 | L-0T g.O€ GE-GI | OG-GI | O1-GT | G6-TT | 8-T1 | GL-1T | 09-TT | OG-TI | G&-TT | G%-IT |] ET-IT | 00-TT | 06-01 | CL-0L | C9-0T 0-08 66 |86 | 46/96 | ¢E | PE! Ses oS LE 0-€ 6S | 8G ae 9G GS “Aquavay ogyoeds Wa ‘AMOLVUOUV] AMIVG AHL NI asQ Boy (‘onuo 8 pucowyry) “AGIAVUY) O1MIOUdG ANV LV NOU SAITIOg IVLO], JO NOLLVINOTVD FHL YOJ— "ATX XXO ATAViL TABLE CXXXI,—For Oorrectine tHe Speciric Gravity or M Decrees or THERMOMETER (fahrenheit). Degrees of see 33) 3a 36 | 36| 37| 38| 30 | 40| 41) 42| 43| 44| 45 | 46| 47| 48| 40] 50| 51 | 52| 63| 54| 55| 56] 57) 58) 59| 60 | a1 | 62 20 19-0 | 19-0 | 19-1 | 19-1 | 19-2} 19-2 | 19-3 | 19:4 | 19-4] 19-5 | 19-6 | 19-7 | 19-8 | 19-9 | 19-9 | 20-0 | 20-1 | 20-2 21 19:9 | 20-0 | 20-0 | 20-1 | 20-2 | 20-2 | 20-3 | 20-3 | 20-4 | 20°5 | 20-6 | 20-7 | 20°8 | 20-9 | 20-9 | 21-0 | 21:1 | 21-2 22 20-9 | 21-0 | 21-0 | 21-1 | 21-2 | 21-2 | 21-3 | 21-3 | 21-4 | 21°5 | 21-6 | 21-7 | 21-8 | 21-9 | 21-9 | 22-0 | 22-1 | 22-2 23 21°9 | 22-0 | 22-0 | 22-1 | 22-2 | 29-2 | 29-3 | 22-3 | 22-4 | 20-5 | 22-6 | 22-7 | 22:8 | 22-8 | 22-9 | 23-0 | 23-1 | 23-2 24 22-9 | 22-9 | 23-0 | 23-1 | 23-2 | 23-2 | 23-3 | 23-3 | 23-4 | 23-5 | 23°6 | 23°6 | 23-7 | 23-8 | 23-9 | 24-0 | 24-1 | 24-2 25 23-8 | 23-9 | 24-0 | 24-0 | 24-1 | 24-1 | 24-2 | 24-3 | 24-4 | 24-5 | 24-6 | 24-6 | 24-7 | 24-8 | 24-9 | 25-0 | 25-1 | 25-2 26 248 | 24-9 | 24:9 | 25-0 | 25-1 | 25-1 | 25-2 | 25-2 | 25-3 | 25-4 | 25-5 | 25°6 | 25-7 | 25-8 | 25-9 | 26-0 | 26-1 | 26-2 27 25°8 | 25°9 | 25-9 | 26-0 | 26-1 | 26-1 | 26-2 | 26-2 | 26-3 | 26-4 | 26-5 | 26-6 | 26-7 | 26-8 | 26-9] 27-0 | 27:1 | 27:3 28 26-7 | 26-8 | 26-8 | 26-9 | 27-0 | 27-0 | 27-1 | 27-2 | 27°3 | 27-4 | 27°5 | 27-6 | 27-7 | 27°8 | 27-9 | 28-0 | 28-1 | 28-3 29 27°7 | 27°8 | 27-8 | 27-9 | 28-0 | 28-0 | 28-1 | 28-2 | 28-3 | 28-4 | 28:5 | 28-6 | 28-7 | 28-8 | 28-9 | 29-0 | 29-1 | 29:3 30 28°6 | 28-7 | 28-7 | 28-8 | 28-9 | 29-0 | 29-1 | 29-1 | 29-2 | 29-3 | 29-4 | 29°6 | 29-7 | 29-8 | 29-9 | 30-0 | 30-1 | 30:3 31 ms 295 | 29°6 | 29-6 | 29-7 | 29-8 | 29-9 | 30-0 | 30°1 | 30-2 | 30-3 | 30-4 | 30-5 | 30°6 | 30-8 | 30-9 34-0 | 31-1 | 31-3 32 || 29-7 29-7 29:8 | 29'8 | 299 | 29:9] 30-0 | 30°0 | 301 | 30°2| 30-3 | 30-4 | 30-4 | 305 | 30°5| 30°6 | 30-7 | 30-9] 31-0 | 81-1 | 31-2 31-3 | 31-4] 31-5 | 31-6 | 31-7 | 31-9] 32-0 | 321 | 32-3 33 || 30-6 | 30-6 | 30-7 | 308 | 30-8 | 30-9 | 30-9 | 31-0 | 31-0 | 31-1 | 31-2 | 31-3 | 31-4 | 31-4 | 31-5 | 31-6 | 31-7 | 31-8 | 31-9 | 32-0 | 32-1 | 32-3 | 32-4 | 32:5 | 32°6 | 32-7 | 32-9 | 33-0 | 83-1 | 33-3 84 — |] 31-5 | 31-5 | 31-6 | 31-6 | 31-7 | 31-8 | 31-8 | 31-9 | 32-0 | 32-0 | 32-1 | 32-2 | 32°3 | 32-4 | 32-5 | 32-6 | 32-7 | 32°8 | 32-9 | 33-0 | 33-1 | 33-3 | 33-4 | 33-5 | 33°6 | 33-7 | 33-9] 84-0 | 34-1 | 34-3 35 || 324 | 32-4 | 32-5 | 32°5 | 32-6 | 32-7 | 32-7 | 32:8 | 32-9 | 32-9 | 33-0 | 33-1 | 33-2 | 33-3 | 33-4 | 33-5 | 33-6 | 33-7 | 33-8 | 33-9 | 34-0 | 34-2 | 34-3 | 34-4 | 34-5 | 34-7 | 34-8 | 35-0 | 35-1 | 35-3 36 || 33-3 | 33-4 | 33-4 | 33°5 | 33-5 | 33°6 | 33-6 | 33°7 | 33°8 | 33-9 | 34-0 | 34-1 | 34-2 | 34-3 | 34-4 | 34-5 | 34-6 | 34-7 | 34-8 | 34-9 | 35-0 | 35-1 | 35-3 | 35-4 | 35°5 | 35-7 | 35-8 | 86-0 ce ‘ ‘ YRAVITY OF MILK ACCORDING TO TEMPERATURE. a ee ee (a R (Fahrenheit). Degrees of ee Lactometer. 0 | 6 | 62) 63 | 64) 65 | 66 | 67] 68| 69) 70\ 71 | 72| 73| 74| 75| 76| 77| 78| 79) 80] 81 | 82) 83} 84} 85 )°0 | 20:1 | 20-2 | 20-2 | 2):3 | 20-4 | 20-5 | 20-6 | 20-7 | 20-9 | 21-0 | 21:1 | 21-2 | 21°3 | 21-5} 21°6| ... aaie 4 ied ‘i sais ea ee Be on 20 1:0 | 21-1 | 21-2 | 21-3 | 21-4 | 21-5 | 21-6 | 21-7 | 21-8 | 22-0 | 22-1 | 22-2 | 22-3 | 22-4 | 22-5 | 22-6] ... we des ia ne sa vas ba 45 21 2° | 22°] | 22-2 | 22°3 | 22-4 | 225 | 22-6 | 22-7 | 22-8 | 23-0 | 23-1 | 23-2 | 23-3 | 23-4 | 23-5 | 23-7]... a Aen aie ast ats oe | ae Bad si 22 3°O | 23:1 | 23-2 | 23:3 | 23-4 | 28-5 | 23-6 | 23-7 | 23-8 | 24-0 | 24-1 | 24-2 | 24-3 | 24-4] 24-6] 24-7]... wee fdas re an age sae dehsea ais ite 23 AO | 24:1 | 24-2 | 24:3 | 24-4 | 24-5 | 24-6 | 24-7 | 24-9 | 25-0 | 25-1 | 25-2 | 25-3 | 25°5 | 25-6 | 25-7]... aes tei Be a ia ca a a ae 24 9°O | 25-1 | 25-2 | 25°3 | 25-4 | 25-5 | 25-6 | 25-7 | 25-9 | 26-0 | 26-1 | 262 | 26-4 | 26-5 | 26-6 | 268] ... ‘ie hes wis os hiss Daan eer ee aie 25 30 | 261 | 26-2 | 26-3 | 26-5 26°6 | 26-7 | 26'S | 27-0 | 27-1 | 27-2 | 27°3 | 27-4 | 27°5 | 27-7 | 27°8 | 27°9 | 28:0 | 28-2 | 28-3 | 28-4 | 28°6 | 28-7 | 28°9 | 29°0 | 29-2 26 10 | 27°1 | 27°83 | 27:4 | 27-5 | 27-6 | 27-7 | 27-8 | 28-0 | 28-1 | 28-2 | 28-3 | 28-4 | 28-6 | 28-7 | 28-9 | _9:0 | 29:1 | 29+2 | 29-4 | 29°5 | 29°6 | 29°8 | 30°0 | 30'1 | 30°3 27 3° | 28°1 | 28-3 | 28-4 | 28°5 | 28-6 | 28-7 | 28-8 | 29-0 | 29°] | 29-2 | 29-4 | 29°5 | 29-7 | 29°8 | 29:9 | 30°0 | 30-2 | 30°3 | 20-4 | 30°6 | 30°7 | 30°8 | 31-0 | 31-2 | 31-4 28 yO | 29-1 | 29-3 | 29-4 | 29-5 | 29-6 | 29-8 | 29-9 | 30-1 | 30-2 | 30°3 | 30°4 | 30°5 | 30-7 | 30-9 | 31°0 | 31:1 | 31°3 | 31-4] 31°5 | 31°7 | 31:9 | 32-0 | 32-2 | 32°3 | 32°5 29 )O | 30°1 | 30-3 | 30-4 | 30°5 | 30-7 | 30-8 | 30-9 | 31-1 | 31-2 | 31:3 | 81°5 | 31-6 | 31-8 | 31-9 | 32-1 | 32-2 | 32-4 | 32-5 | 32°6 | 32°8 | 33-0 | 33-1 | 33°3 | 33°4 | 33°6 30 0 | 311 | 31°3 | 31-4 | 31-5 | 31-7 | 31-8 | 32-0 | 32-1 | 32-2 | 32-4 | 32°5 | 32°6 | 32-8 | 33-0 | 33-2 | 33-3 | 33-4 | 33 6 | 33-7 | 33-9 | 34-0 | 34:2 | 34-4 | 34°5 | 34-7 31 0 | 32-1 | 32°3 | 32-5 | 32 6 | 32-7 | 32-9 | 33-0 | 33-2 | 33-3 | 33-4 | 33-6 | 83-7 | 33-9 | 34-1 | 34:3 | 34:4 | 34:5 | 34-7 | 34°8 | 35-0 | 35-1 | 35:3 | 35°5 | 35-6 | 35°8 32 0 | 33-1 | 33-3 | 33-5 | 33-6 | 33-8 | 33-9 | 34-0 | 34-2 | 34-3 | 34-5 | 34-6 | 34-7 | 34-9 | 35-1 | 35-3 | 35-4 | 35-6 | 35S | 36-0 | 36:1 | 36-3 | 36-4 | 36-6 | 36-7 | 36-9 33 kO | 34:1 | 34:3 | 34:5 | 34-6 | 34-8 | 34-9 | 35-0 | 35-2 | 35°3 | 35-5 | 85°6 | 35-8 | 36-0 | 36-2 | 36-4 | 36°5 | 36-7 | 36-9 | 37-0 | 37-2 | 37°3 | 37°5 | 377 | 37°9 | 38-1 34 0 | 35:1 | 35°3 | 35°5 | 35-6 | 35-8 | 35-9 | 36-1 | 36-2 | 36-4 | 36-5 | 36-7 | 36°8 | 37:0 | 37:2 | 37-4) ... ved aft Wgesr Pasa Viegas ace of raee |” cies 35 oe vee a ie a a EE ET TABLE CXXXII.—For THe 2°0 21 1°20 || 1°32 | 1:44 | 1°56 | 1°68 | 1:80 | 1:92 | 2-04 | 2-16 22 | 20 2°52 Specific Gravity. | Vane of 1:2 Fat. welteue ee D | 22°0 5652 22°5 577 23°0 5901 23°5 | 6:027 24°0 6°153 24°5 6°278 25°'0 6°402 25°'5 6°527 26°0 6-652 26°5 6°776 27°0 6-900 27°5 7025 28°0 7150 28°5 7274 29°0 | 7:°397 29°5 7522 30°0 | 7:647 30°'5 7771 31:0 7895 31°5 8-018 32°0 8°140 32°5 8264 33°0 8387 33°5 8°509 34:0 8°631 34°5 8°755 35°0 8°878 35°'5 9-000 36°0 9°122 36°5 9°244 37°0 9366 37°5 9°488 6°13 6°26 6°38 6°51 6°63 6°76 6°88 7-01 7:13 7°26 7°38 751 7°63 7°75 7°88 8:00 8:13 8°25 8°38 8°50 8-62 8°74 8:87 8:99 911 9°24 9°36 9°48 9°60 9°72 9°85 9:97 6:25 6°38 6°50 6°63 6°75 6°88 7:00 7:13 7°25 7°38 7°50 7°63 7°75 7 87 8-00 8-12 8°25 8°37 8°50 862 8-74 8°86 8:99 9°11 9°23 9°36 9°48 9°60 9°72 9°84 9:97 10-08 6:37 6°50 6°62 6°75 6°87 7-00 7:12 7°25 7:37 7°50 7°62 7°75 7°87 7:99 8:12 8:24 8°37 8°49 8-62 8-74 8°86 6:49 6°62 6°74 6°87 6:99 7:12 724 7°37 7°49 7°62 7:74 7:87 7:99 8:11 8:24 8°36 8:49 8°61 8°74 8°85 8-98 6°61 6°74 6°86 6-99 711 7°24 7°36 7:49 7°61 774 7°86 7:99 8:11 8°23 8°36 8°48 8°61 8°73 8°86 8°98 9°10 8:98] 9:10] 9:22 9-11 9°23 9°35 9-48 9°23 9°35 9°47 9°60 9°35 9°47 9°59 9°72 9°60} 9°72) 9°84 9°72 9°84 9°84 9:96 9:96 10°08 9-96 | 10-08 | 10-20 10-09 | 10°21 | 10°21 | 10°33 Heese 10°33 | 10°45 6°73 6°86 6-98 71h 7°23 7°36 7:48 761 7:73 7°86 7:98 8-11 8°23 8°35 8-48 8:60 8°73 8°85 8-98 9°10 9°22 9°34 9°47 9°59 9°71 9°84 9 96 10°08 10 20 10°32 10°45 10°57 6-85 || 6-97) 7:09) 7:21] 7:33} 7-45] 7:57] 7-69] 7-81] 7:93] 8-05 8:17] 8:29] 8-41} 8:53] 8 6°98 || 7°10) 7:22} 7:34] 7:46} 7:58] 7°70] 7:32] 7:94] 8-06] 8-18]] 830] 3-42 8:54] 866] 8 7:10 || 7°22) 7:34) 7:46] 7:58] 7°70] 7-82] 7-94] 8-06] 8-18] 8-30] 8-42 8°54] 8°66] 8°78] 8 7°23) 7°35) 7°47) 7°59] 7°71] 7:83] 795| 8-07] 819] 8-31] 8-431) 8-55 8°67} 879} 8-91] 9 7°35 | 7:47) 7°59] 7°71] 7:83} 7:95] 8-07] 8-19] 8-31] 8-43] 8-55 8:67] 879] 8:91] 9:03] 9 9 9 9 9 748] 7:60} 7°72] 7°84] 7:96] 8-08] 8-2 832] S44] 856] 8-68]/ 8-80] 8:92] 9°04] 9-16 7°60 || 7°72) 7°84} 7:96] 8-08} 8-20] 8-32] 844] 8-56] 8-68] s-s0]] 8-92 9:04] 9°16} 9°28 7°73! 7°85] 7:97) 8-09] 821] 833] 845] 8-57] 869] 8-81] 8-93 9°05} 9:17) 9:29] 9-41 7:85 | 797] 8°09] 8-21} 833] 8-45] 857] 8-69] 881] 8-93] 9-05 9:17) 929] 941} 9-53 7°98 || 8:10] 8°22] 8:34] 8-46] 8-58] S-7 8°82) 8:94} 9°06} 9:18]) 9:30] 9-42] 9-54] 9-66] 9: 810 |} 8:22} 8:34] 8-46] 8-58] 8-70] 852] 8-94] 9-06] 9-18] 9:30 9°42] 9:54) 966] 9:78] 9: 8-23 || 8°35] 847] 859} 8-71) 8-83] 895] 9-07] 9:19] 9:31] 9-43] 9-55 9°67] 979} 9:91] 10° 8°35] 8:47} 859) 8-71) 883] 8-95] 907] 9:19] 9:31] 9-48] 9-55 9°67] 9°79] 9°91] 10-03] 10: 8-47} 8°59} 871] 8-83] 8:95] 9-07] 9:19] 9:31] 9-43] 9:55] 9-67 9°79} 9°91} 10 03} 10°15] 10: 8-60} 8°72} 884] 8-96] 9:08] 9-20] 9:32] 9-44] 9:56] 9-68] 9-80 9°92 | 10-04 | 10°16 | 10°28 | 10° 872 |) 884] 8°96] 9-08} 9:20] 9-32] 9-44] 9:56] 9-68] 9-80] 9-92 10-04 | 10°16 | 10-28} 10°40} 10- 8°85 || 8°97} 909} 9:21} 9:33] 9-45] 9:57] 9:69] 9:81] 9-93] 10-05 10°17 | 10°29 | 10°41 | 10°53 | 10- 8°97 || 9°09} 9°21] 9:33] 9-45] 9-57] 9-69] 9-81] 9-93] 10-05 | 10-17 10°29 | 10°41 | 10-53 | 10°65 | 10° 910 }} 9°22] 9:34] 9-46] 9°58] 9-70] 9:82] 9-94] 10-06] 10-18] 10-30 10°42 | 10°54 | 10-66 | 10°78 ] 10° 9°22 ]) 9°34) 9-46] 9-58} 9°70} 9-82] 9-94] 10-06 | 10:18 | 10-30 | 10-42 10 54 | 10°66 | 10°78 | 10°90 | 11. 9°34] 9°46] 9°58} 9°70} 9:82] 9-94] 10-06] 10°18 | 10-30 | 10-42 | 10-54 10°66 | 10°78 | 10°90 | 11-02 | 11- 946) 958] 9°70] 9-82] 9:94] 10-06] 10-18] 10°30 | 10-42 | 10°54 | 10-66 10°78 | 10-90 | 11-02 | 11°14} 11° 959 971) 9°83} 9-95] 10-07} 10-19] 10:31] 10-43 | 10°55 | 10°67 | 10-79 10°91 | 11-03 | 11°15 | 11-27] 11: 9°71 || 9°S3] 9°95 | 10-07 | 10-19 | 10-31 | 10-43 | 10°55 | 10-67 | 10-79 | 10-91 11°03 | 11°15 | 11°27} 11:39] 11°: 9°83 || 9°95 | 10°07 | 10°19 | 10-31 | 10-43 | 10-55 | 10°67 | 10-79 | 10-91 | 11-03 11°15 | 11-27 | 11°39} 11-51 | 11° 9°96 || 10°08 | 10°20 | 10°32] 10-44 | 10-56 | 10-68 | 10-80 | 10-92 | 11-04 11°16 |} 11°28 | 11-40 | 11-52 | 11°64 | 11 10°08 |] 10°20 | 10°32 | 10-44 | 10-56 | 10-68 | 10:80 | 10-92 | 11-04] 11-16 | 11-28 11°40 | 11°52 | 11°64] 11°76 | 11° 10°20 || 10°32 | 10°44 | 10°56 | 10-68 | 10-80 | 10-92 | 11-04 | 11°16 | 11-28 11°40 |) 11°52 | 11°64 | 11-76 | 11-88 | 124 10°32 || 10°44 | 10°56 | 10-68 | 10°80 | 10-92 | 11-04 | 11°16 | 11-28 | 11°40 11°52 | 11°64 | 11°76 | 11-88 { 12-90 | 12: 10°44 |] 10°56 | 10°68 | 10°80 | 10°92 | 11-04] 11°16 | 11°28 | 11-40 | 11°52 | 11-64 11°76 | 11°88 | 12-00 | 12°12 | 12: 10°57 || 10°69 | 10°81 | 10-93 | 11-05 | 11°17 | 11-29 | 11-41 | 11°53 | 11-65 11°77 || 11°89 | 12°01 | 12°13 | 12-25 | 12. 10°69 || 10°81 | 10-93 | 11-05 | 11-17 | 11-29] 11-41 | 11°53 | 11-65 11°77 | 11°89 || 12-01 | 12-13 | 12-25 | 12-37 | 12. II.—For tHe Catcunation or Toran Sormps From Far ann Spgciric Gravity (Richmond's Formula). Fav PER CENT, 3 | 3°60 | | 3°72 | 3°84 | 3-96 | 4-08 4 20 | 329 | 8:41 8°54 8°66 8-79 8:91 9°04 9°16 9°29 9-4) 9°54 9-66 9°79 9-91 10 03 10°16 10°28 10°41 10°53 10°66 10°78 10°90 11-02 11:15 11:27 L139 11°52 11°64 11°76 11°88 12-00 1S 12°25 11:76 11°88 12-00 12°12 12°24 12°37 12°49 8°77 8:90 9°02 9°15 9°27 9°40 9°52 9°65 9°77 9°90 10°02 10°15 10°27 10°39 10°52 10°64 10°77 10°89 11:02 ll-l4 11°26 11°38 11°51 11°63 11°75 11°88 12°00 12°12 12°24 12:36 12°49 12°61 4°32 — 3°30 10°01 10-14 10°26 10°39 10°51 10°63 10°76 10°88 11°01 11°13 11:26 11°38 11°50 11°62 11°75 11°87 11:99 12°12 12:24 12°36 12°48 12°60 12°73 12°85 TotaL SoLIpS PER CENT, | 4°56 4°68 5'0 a ww | 6-00 12°60 12°72 12°85 12°97 9GL) 9°73 | 974 | 9-86 | 9-99 10°11 10°24 10°36 10-49 10°61 10-74 10°86 10-99 lll] 11°23 11°36 11:48 11°61 11-73 11-86 11:98 12-10 12-22 12°35 12°47 12°59 12-72 12-84 12-96 13°08 13-20 13°33 | 13-45 9°86 9-98 10°11 10°36 10°48 10°61 10°73 10°86 10°98 Il-ll 11°23 11°35 11°48 11°60 11:73 11°85 11°98 12°10 12:22 12°34 12:47 12°59 12°71 12°84 12°96 13°08 13°20 13°32 13°45 13°57 — Oo to ION 10°23 | 9°85 9-98 10°10 10-23 10°35 10-48 10°60 10°73 10°85 10-98 11-10 11-23 11°35 11-47 11-60 11°72 11°85 11-97 12-10 12-22 12°34 12°46 12°59 12-71! 12-83 12-96 13-08 13-20 13°32 13-44 13-57 — 9°97, 10:16 10:22 10°35 10°47 10°60 10°72 10°85 10:97 11:10 11:22 11°35 11°47 11°59 11°72 11°84 11:97 12-09 12-22 12°34 12°46 12°58 12°71 12°83 12°95 13-08 13°20 13°32 13°44 13°56 13°69 13°81 10°09 10°22 10°34 10°47 10°59 10°72 10°84 10°97 11:09 11°22 11°34 11°47 11°59 11-71 11°84 11°96 12-09 12:21 12°34 12:46 12°58 12-70 12°83 12°95 13°07 13°20 13 32 13°44 1356 13 68 13°81 13°93 10°21 10°34 10°46 10°59 10°71 10°84 10°96 11-09 11°21 11°34 11:46 11:59 P71 11°83 11:96 12-08 12°21 12°33 12°46 12°58 12°70 12-82 12°95 13:07 13:19 13°32 13°44 13°56 13°68 13°80 13°93 14-05 10°33 10°46 10°58 10°71 10°83 10°96 11°08 11:21 11°33 11°46 11°58 11-71 11°83 11°95 12-08 12-20 12°33 1245 12°58 12°70 12°82 12:94 13:07 13°19 13°31 13°44 13°56 13°68 13*50 13-92 14:05 14:17 10°57 70 32 10-95 I]4 Ja 11 11: i lj ll‘ 111-95 || 12°97 12°19 12:32 12:44 | 12-57 12:99 (12:82 12-94 | 13°06 13°18 13°31 |, :13°43 | 13-55 13°68 13°80 13°92 14°04 14°16 14-29 14°41 | 19°69 | 19°82 | 110-94 11-07 Ui19 | | 11°32 | LL-44 | 11°57 | 11-69 j AL-s2 | 31-94 12°07 12-19 12°31 12-44 12°69 12°81 12°94 13°06 13°18 13°30 13°43 13°55 13°67 13°80 13°92 14:04 14:16 14:28 14°41 14°53 12°56 | 10°81 10°94 11-06 11:19 1 11°31 11-44 11°56 11°69 11°81 | 11-94 12-06 12°19 12°31 12°43 12°56 12°68 12°81 12°93 13-06 13:18 13°30 13°42 13°55 13°67 13°79 13-92 14-04 14°16 14:28 14°40 14°53 14°65 10°93 | 11-06 / 11-18 11°31 11-43 11°56 11-68 11°81 11-93 12-06 12-18 12°31 12-48 12°55 12-68 12°80 12-93 13°05 13°18 13°30 13°42 13-54 13-67 13°79 13-91 14-04 14:16 14-28 14-40 14:52 14-65 14-77 1105 11-18 11°30 11°43 11°55 11°68 11°80 11°93 12°05 12°18 12°30 12°43 12°55 12°67 12°80 12°92 13-05 13°17 13°30 13°42 13°54 13°66 13°79 13°91 14:03 14°16 14:28 14:40 14°52 14-64 14°77 14°89 11:17 11°30 11-42 11°55 11°67 11°80 11°92 12°05 12°17 12°30 12°42 12°55 12°67 12-79 12-92 13:04 13:17 13°29 13°42 13°54 13°66 13°78 13°91 14:08 14°15 14:28 14:40 14°52 14:64 14°76 14°80 15°01 11 ll ll 11°67 11°79 11-92 12-04 12°17 12°29 12°42 12°54 12°67 12°79 29 “42 12°91 | 13-04 13°16 13-29 | 13°41 12°54 13°66 13°78 13°90 14°03 14°15 14:27 14°40 14°52 14°64 14°76 14°88 1501 15:13 54 | 1141 1154] 11°66 11°79 11°91 12-04 12°16 12-29 12-41 12°54 12°66 12°79 12°91 13°03 13°16 13°28 13°41 13°53 13°66 13°78 13:90 14:02 14°15 14:27 14°39 14°52 14°64 14°76 14°88 15:00 15°13 15°25 11°53 | 11°66 11°78 11:91 | 12:03 12°16 12°28 12°41 12°53 12°66 12-78 12°91 13°03 13°15 | 1328 13°40 13°53 13°65 13°78 13°90 14:02 14:14 14:27 14°39 14°51 14°64 14°76 14°88 15:00 15:12 15:25 15°37 | | 13°89 14:02 14:14 14:26 14°38 14°51 14°63 14°75 14:88 15:00 15°12 15°24 15°36 15°49 15°61 11°89 12:02 1214 | 12-27 12°39 12°52 12°64 12°77 12°89 13°02 13:14 13°27 13°39 13°51 13°64 13:76 13°89 14:01 14-14 14°26 14°38 14°50 14°63 14°75 14°87 15°00 15:12 15:24 15°36 15°48 15°61 15°73 12-01 12:14 12°26 12°39 12°51 12°64 12°76 12°89 13°01 13°14 13°26 13°39 13°51 13°63 13°76 13°88 14°01 14:13 14°26 14°38 14:50 14°62 14°75 14°87 14°99 15°12 15°24 15°36 15°48 15°60 15°73 15°85 ‘3 5°4 | 5'5 | 56 59/60] 61 | 62 6'5 = | | 1 0 || 6:12 | 6:24 | 6-36 | 6°48 | 6°60 | 6°72 | 6°84 | 6°96 | 7-08 | 7:20 | 7°32 | 7:44 | 7°56 | 7-68 | 7-80 35 || 11°77 | 11°89 | 12-01 | 12°13 | 12-5 | 12-37 | 12-49 | 12-61 | 12°73 | 12°85 |] 12-97 | 13-09 | 13-21 13°33 | 13-45 8 |) 11°90 | 12-02 | 12-14 | 12-26 | 12-38 | 12-50 | 12-62 | 12-74 | 12-86 | 12-98 || 13-10 | 13-22 | 13+34 i346 | 13-58 N) |) 12-02 | 12-14 | 12-26 | 12°38 | 12-50 | 12-62 | 12-74 | 12-86 | 12-98 | 13-10 || 13-22 | 13-34 | 13-46 13°58 | 13-70 DIFFERENCE TABLE. 3 |) 12-15 | 12-27 | 12°39 | 12°51 | 12°63 | 12-765 | 12-87 | 12-99 | 13-11 | 13-23 || 13-35 | 13-47 | 13-59 13°71 | 13°83 5 || 12°27 | 12°39 | 12°51 | 12-63 | 12-75 | 12-87 | 12-99 | 13-11 | 13-23 | 13-35 || 13-47 | 13-59 13°71 | 13°83 | 13-95 8 |] 12°40 | 12-52 | 12-64 | 12-76 | 1288 | 13-00 | 13-12 | 13-24 | 13-36 | 13-48 |] 13-60 | 13-72 | 13-84 13°96 | 14-08 O || 12°52 | 12°64 | 12-76 | 12-88 | 13-00 | 13-12 | 13-24 | 13-36 | 13-48 | 13-60 || 13-72 | 13-84 | 13-96 | 14-08 14:20 3 || 12°65 | 12°77 | 12-89 | 13-01 | 13-13 | 13-25 | 13-37 | 13-49 | 13-61 | 13-73 |] 13-85 | 13-97 | 14-09 | 14-21 14:33 5 |) 12°77 | 12°89 | 13-01 | 13-13 | 13-25 | 13-37 | 13-49 | 13-61 | 13°73 | 13-85 |] 13-97 | 14-09 | 14-21 | 14-33 14°45 8 || 12-90 | 13°02 | 13:14 | 13-26 | 13-38 | 13-50 | 13-62 | 13-74 | 13-86 | 13-98 || 14-10 | 14-22 | 14-34 | 34-46 14:58 0 |) 13-02 | 13°14 | 13-26 | 13°38 | 13-50 | 13°62 | 13-74 | 13-86 | 13-98 | 14-10 |] 14-22 | 14-34 | 14-46 | 14-58 14°70 13°15 | 13°27 | 13-39 | 13°51 | 13°63 | 13°75 | 13-87 | 13-99 | 14-11 | 14-23 |] 14-35 | 1447 | 14-59 | 14-71 | 14-83 13°27 | 13°39 | 13°51 | 13°63 | 13°76 | 1387 | 13-99 | 14-11 | 14-23 | 14°35 |] 14-47 | 14-59 | 14°71 | 14-93 14°95 13°39 | 13°51 | 13°63 | 13°75 | 13-87 | 13-99 | 14-11 | 14-23 | 14-35 | 14-47 |] 14:59 | 14-71 | 14-83 | 14-95 15°07 13°52 | 13°64 | 13°76 | 13°88 | 14-00 | 14°12 | 14-24 | 14-36 | 14-48 | 14-60 |] 14-72 | 14-84 | 14-96 | 15-08 | 15-20 13°64 | 13°76 | 13°58 | 14-00 | 14:12 | 14-24 | 14-36 | 14-48 | 14-60 | 14-72 || 14-84 | 14-96 | 15-08 | 15-20 | 15°32 13°77 | 13°89 | 14-01 | 14°13 | 14-25 | 14:37 | 14-49 | 14-61 | 14-73 | 14-85 || 14-97 | 15-09 | 15-21 | 15-33 | 15-45 13°89 | 14°01 | 14°13 | 14°25 | 14:37 | 14-49 | 14-61 | 14-73 | 1485 | 14-97 || 15-09 | 15-21 | 15-33 | 15-45 | 15°37 14°02 | 14°14 | 14°26 | 14°38 | 1450 | 14:62 | 14-74 | 14-86 | 14-98 | 15-10 || 15-22 | 15-34 | 15-46 | 15°58 | 15-70 14°14 | 14°26 | 14°38 | 14°50 | 14-62 | 14-74 | 14-86 | 14-98 | 15-10 | 15-22 |] 15-34 | 15-46 | 15-58 | 15-70 | 15-82 14°26 | 14°38 | 14°50 | 14-62 | 14°74 | 14-86 | 14-98 | 15-10 | 15-22 | 15°34 |] 15-46 | 15-58 | 15-70 | 15-82 | 15-94 14°38 | 14°50 | 14°62 | 14°74 | 14-86 | 14-98 | 15-10 | 15-22 | 15-34 | 15-46 || 15°58 | 15-70 | 15°82 | 15-94 | 16-06 14°51 | 14°63 | 14°75 | 14°87 | 14-99 | 15-1] | 15-23 | 15-35 | 15-47 | 15°59 || 15-71 | 15-83 | 15-95 | 16-07 | 16-19 14°63 | 14°75 | 14°87 | 14-99 | 15-11 | 15-23 | 15-35 | 15-47 | 15-59 | 15°71-]] 15-83 | 15-95 | 16-07 | 16-19 | 16-31 14°75 | 14°87 | 14°99 | 15-11 | 15-23 | 15°35 | 15-47 | 15-59 | 15-71 | 15°83 || 15-95 | 16-07 | 16-19 | 16-31 | 16-43 14°88 | 15°00 | 15°12 | 15-24 | 15°36 | 15-48 | 15-60 | 15-72 | 15-84 | 15°96 || 16-08 | 16-20 | 16-32 | 16-44 | 16-56 15°00 | 15°12 | 15°24 | 15-36 | 15-48 | 15-60 | 15-72 | 15-84 | 15-96 | 16-08 |] 16-20 | 16-32 | 16-44 | 16-56 | 16-68 15°12 | 15°24 | 15°36 | 15-48 | 15°60 | 15-72 | 15-84 | 15-96 | 16-08 | 16-20 |] 16-32 | 16-44 | 16-56 | 16-68 | 16-80 15°24 | 15°36 | 15°48 | 15-60 | 15°72 | 15-84 | 15-96 | 16-08 | 16-20 | 16-32 || 16-44 | 16-56 | 16-68 | 16-80 | 16-92 15°36 | 15°48 | 15°60 | 15-72 | 15-84 | 15-96 | 16-08 | 16-20 | 16-32 | 16-44 || 16-56 | 16-68 | 16-80 | 16-92 | 17-04 15°49 | 15°61 | 15°73 | 15°85 | 15-97 | 16-09 | 16-21 | 16-33 | 16°45 | 16°57 |] 16-69 | 16-81 | 16-93 | 17-05 | 17°17 15°61 | 15°73 | 15°85 | 15-97 | 16-09 | 16-21 | 16-33 | 16-45 | 16°57 | 16-69 |] 16-81 | 16-93 | 17-05 | 17-17 | 17-29 ee ee, ee ee ee ee ae ee Ge. oe Oe. Specific Gravity. TABLE CXXXIII.—For tHe C O1 | O2 | 03 06 | O'7 | O88 | O'9 | 1:0 11 12 | 6-21 | 6:33 | 6:45 | 656 | 668} 679} 691) 7-03] 714] 7:26) 7:38] 7-49] 7-61] 7-73] 7-84] 76] 8-07} 8-19] 8-31 8-421 8:54) 8°66 6°34 | 6:46 | 6°57 | 669 | G80) 692) 7-04) 715) 7-27] 7:39] 7:50) 7:62) 7:74| 7:85] 7-97] 809! 8-20] 8-32 8-43] 8:55] 8°67] 8-78 6:47 | 6°58 | 6-70 | 682 | 693°) 7:05] 7:16] 7:28] 7:40) 7-51 | 763 775) 786) 7:98) 810] 821] 8-33] 845] 8-56] 8-68 || 8-77] 3-91 6:59 | 6-71 | 6:85 | 694 | 7:06) 7:18] 7:29] 7:41] 7:53! 7-64 | 776) 7°87 | 7°99] 8-11) 822] 834] 8-46] 8-57} 8-69] 8-81] 8-92! 9-04 6-72 | 6:84 | 6-95 707 | 7:19} 7:30] 7:42] 7°54] 7:65] 7°77 | 788 | 800} 812} 823) 8-35] 847] 8-58] 8-70} 8:82! 8-93] 9:05! 9-16 6°35 | 6°96 | 7-05 | 7-20] 7:31) 7:43] 755| 766) 7-78] 7:90) sol] 813] 8-24] 8-36] 8-48 859) 8-71] 8°83} 8-94) 9:06) 9:18] 9-29 6°97 | 7:09 | 7°21 | 7:32 | 7:44} 7:56) 7:67] 7:79] 7-91) 8-02 i S14} 8-25) 837] 849] 8-60] 8-72] 8-84] 8-95] 9-07] 9:19|| 9:30} 9-42 7:10 | 7-22 | 7:33 | 745 | 7:57 | 7:68| 7°80} 7:92] 8-03) 8:15 | 827] 8:38] 8-50] 8-61] 8-73] 8-85 8°96] 9:08} 9:20] 9-31 |/ 9-43} 9:55 7°23 | 7°34 | 7-46 | 708 | 7°69! 7:81} 7:93] 8-04} 8-16] 8-28] 8:39) 851] 8-63] 8-74] 8:86] 8-97 9:09} 9:21] 9°32] 9-44] 956] 9-67 7°36 | 7:47 | 7°59 | 770 | 782) 7:94) 8-05] 8:17) 8-29) 8-40) 852} 8-64] 8-75] 887] 8-99] 9-10 9:22) 9:33] 9:45] 9°57]|/ 9:68] 9-80 748 | 760 | 7:72 7:83 | 7°95] 8-06] 8:18) 8:30] 8-41] 8-53 | 865 | 876] 888} 9:00} 9:11] 923] 9:34] 9-46} 9-58] 9-69 || 9-81 9:93 761 | 7:73 | 7°84 7:96 | 8-08] 8:19} 8-31] 842) 8-54) 8-66) 8-77] 8-s9} 9-01! 912] 9-24 9°35) 9-47] 959} 9-70} 9-82 || 9-94 | 10-05 774 | 785 | 7:97 | 8:09 | 820] 8:32] 843! 8-55] 8-67) 8-78} 8:90} 9-02} 9:13] 9-25] 9-37 9-45) 960] 9°72] 9:83} 9-95 || 10-06 | 10-18 7:86 | 7:98 | 8:16 | 8-21 | 833] 8-45] 8-56] 8-68 8-79; 891 | 9°03} 914) 9:26) 938] 9-49] 9-61) 9:73} 9-84] 9-96] 10-08 |] 10-19 10°31 7:99 | S11 | 8:22 8°34 | 8-46) 8:57] 869] 8-81] 8-92 9-04, 915) 927) 939) 950} 9:62} 9-74} 9-85] 9-97] 10-09 | 10-20 | 10-32 10°43 8:12 | 8-23 | 8°35 | 847 | 8-58} 8-70] 8-82] 8-93] 9-05] 9-17]| 9-28] 9-40] 9-51 9°63} 9°75) 9-86] 9-98} 10-10} 10-21 | 10:33 || 10-45 | 10°56 S24 | 8:36 | 8-48 | 859 | 8-71] 8-83} 8-94] 9:06} 9:18] 929]| 9-41] 9:52] 9-64 9°76 | 9°87} 9-99} 10-11 | 10-22 | 10-34 | 10-46 || 10°57 | 10-69 8°37 | 8-49 | 860 | 872 | 884] 3-95] 9-07} 9:19} 9:30} 9-42]) 9:54] 9°65] 9°77 9°88 | 10°00 | 10-12 | 10:23 | 10-35 | 10-47 | 10-58 || 10°70 | 10-82 8°50 | 8°61 | 8°78 | 885 | 896] 9:08} 9-20} 9-31] 9-43] 9:55 |] 9:66] 9-78] 9-89 10°01 | 10°13 | 10-24 | 10-36 | 10-48 | 10°59 | 10°71 |] 10°83 | 10-94 8°62 | 8-74 | 8°86 | 8:97 | 9:09} 9-21] 9-32] 9-44] 9-56] 9-67]! 9-79] 9-91 | 10-02 10-14 | 10-25 | 10°37 | 10-49 | 10°60 | 10-72 | 10-84 || 10-95 11-07 875 | 8S7 | 8:99 | 9:10 | 9-22] 9:33) 9-45} 9:57! 9-68] 9-80] 9-92] 10-03 | 10-15 10°27 | 10°38 | 10°50 | 10°61 | 10°73 | 10-85 | 10-96 || 11-08 | 11-20 888 | 9:00 ! 9:11 | 9:23 | 9:35! 9-46] 958} 9-69] 9-81] 9-93 || 10-04! 10-16 10°28 | 10°39 | 10°51 | 10-63 | 10-74 | 10-86 | 10-97 | 11-09 |! 11-21 11°32 9°01 | 9°12 , 9:24 9°36 | 947} 9:59} 9°70} 9-82] 9-94] 10-05 | 10-17 | 10-29 | 10-40 | 10-32 10°64 | 10°75 | 10°87 | 10-99 | 11-10 | 11-22 || 11-33 | 11-45 913 ; 925 | 9°37 | 9-48 | 9:60} 9-72} 9-83} 9-95] 10-06} 10-18 |] 10:30 | 10-41 10°53 | 10°65 | 10°76 | 10-88 | 11-00 | 11°11 | 11-23 | 11-35 9°26 | 9°38 | 9-49 | 9°61 | 9-73] 9-84] 9-96] 10-08] 10-19] 10°31 || 10-42 | 10-54 10°66 | 10°77 | 10-89 | 11-01 | 11-12] 11-24 | 11-36 | 11-47 9°39 | 9°50 | 9°62 | 9-74 | 9:85] 9-97] 10-09 | 10-20 | 10-32 | 10-44 9°51 | 9°63 | 9°75 | 9°86 | 9-98] 10-10! 10-21 | 10-33 | 10-45 | 10°56 9°64 | 9°76 | 9°87 | 9:99 | 10-11 | 10-22 | 10°34 | 10-46 | 10°57 | 10-69 | | 1 9-40 9°52 | 9°65 9°78 9-91 10-03 10°16 | 10°29 10°41 10°54 10°67 10°79 10°92 11°05 11:18 11°30 11°43 11°56 11°68 —For THE CALCULATION oF ToTaL SoLIpDs FRoM Far AND SPECIFIC GRAVITY (Hehner and Richmond’s Formula). 37 | 3:8 | 3:9 ay 41 | 4:2 8°77 8:90 11} 9-03 9-15 9-28 9-41 2} 9-54 9°66 7 | 9°79 9:92 | 10-04 5 | 10°17 8 | 10-30 1 | 10-42 3} 10°55 6 | 10°68 9| 10-81 2} 10-93 £/11-06 7| 11-19 )} 11°31 »| 11-44 11°57 8:89 9:02 9-14 9°27 9-40, 9°52 9°65 9°78 | 9-9) 10:03 10°16 10°29 10-41 | 1054 10°67 10°79 10°92 11°05 11:18 11°30 11°43 9°24 9°37 9°49 9°62 9°75 9°87 10-00 10°13 10°25 10°38 10°51 10°64 10°76 10°89 11-02 11°14 11°27 11°40 Fat PER CENT. 10°73 10°56 | 10°99 11-11 11°24 ) 10°60 |) j| 9°82 | 9°95 | 10-07 | 10°20 10°33 10°46 10°58 10°71 10°84 10°96 11-09 9:94 10:06 10°19 10°32 10°45 10°57 10°70 10°83 10 95 11-08 11°21 11°33 11°46 11°59 11°72 11°84 11°97 12°10 12-22 12°35 12°48 12°60 12°73 10°17 10:30 10°42 10°55 10°68 10°80 10°93 11-06 11°19 11°31 1l-44 11°57 1] 69 11°82 11°95 12-08 12-20 12:33 12°46 12°58 12°71 12°84 12:96 10°64 | 10°76 10°89 11:02 1114 11°27 11°40 11°52 11°65 11°78 11°91 12:03 12°16 12-29 12-41 12°54 12°67 12°79 12-92 13-05 13°18 13:30 13°43 11°50 11°63 11°76 11°88 12°01 12°14 12:27 12°39 1 11°38 | 10°98 ld) |11-26 11:37 11°49 | 11°75 | 11°87 12:00 | 12-13 12:25 12°38 12°51] 11-62} || 12:52 | 12-64 12°65 | 12°76 || 12-77 | 12-89 12-90 13°03 13°15 13°28 13°41 13:54 13°66 13-02 13°14 13:27 13°40 13:52 13°65 13°78 11°33 11:46 11°59 11°72 11°84 11°97 12°10 12-22 12°35 12°48 12°60 12°73 12°86 | 12-99 13-11 13°24 13°37 13°49 1362 13°75 13°87 14:00 14:13 11°57 11°69 11:82 11°95 12-07 12-20 12°33 12°46 12°58 12°71 12°84 12°96 13:09 13°22 | 13°34 | 13°47 13-60 13°73 13°85 13-98 14°11 14°23 14°36 12:27 12:39 12°52 12°65 12°77 12-90 13°03 13°15 13°28 13°41 | 13°54 13°66 13°79 13-92 14-04 14:17 14°30 14°42 14°55 14:68 14°81 14°93 15:06 13° 13° 13" 13+ 14+ 14:1 14% 14+ 14° 14°€ 14°7 14° 15 15°] la). 11°57 11°69 11°82 11°95 12:07 | 12:20 | 12°33 | 12°46 12°58 12°71 12°84 12°96 13:09 13°22 13°34 13°47 13°60 3°73 3°85 3°98 4-11 4:23 4°36 13°08 13°21 13°33 13°46 13°59 13°72 13°84 13°97 14:10 14:22 14°35 14-48 14-60 14°73 14:86 14°99 15:11 15°24 15°37 15°49 15°62 15°75 15 ‘87 DIFFERENCE TABLE. T | F. T | | om 0-01 01 003 | (002 0-02 0-2 005 «| 003 003 | 03 008 =| o-4 005 | 04 | O10 | 0-05 0-06 | 0:06 0-07 0-07 0-08 0-08 0-09 0-09 0-10 417 USEFUL TABLES, ‘ainsy ysorvou oY} 94¥4 6.0 IO ‘9.0 ‘F-0 ‘T-0 ws ae “ a ‘eAoge orndsy 4sorvou WoIZ CO.9 PIIGNS 8.0 JO ¢.0 on fe He e AOTOG oANSY Ysorvou oy} 07 CO.Q UO Ppv L.Q JO GO SI AMALVAT oytoads oy ul peMID9p OY4 JT — ‘e(. UO ppv Fey “quo aod G).0 JOT Gt : | ' GE-ST | SG-GT | OT-ST | 00-ST | 06-FI | SL-F1 |) $9-FI | OS- FT | OF-FL | OS-FI | SUFI joer 06-€1 | O8-€1 | OL-EU, GG-€T G-DE 1 GB-ST | OL-ST | 00-ST | S8-FT | CL-FI | C9-FI || OS-FI | OF- FT| GS-F1 | SL-FI | CO-FT lai O8-ET | G9-S1 | See! Shel 0.78 OL-ST | 00-S1 | S8-FT | SL-FT | G9-FL | 0G-F1 || OF FT | Sa-FL | ST-FL | CO-FT | O6-€1 | O8-ET | S9-ET | S9-ET | SF-ST | O8-ET gee 00-ST | S8-F1 | GL-FT | $9-FI | 0G-FT | OF-FT |] G&-FT | ST-FT | SO-FT | 06-8T | 08-€T | 99-ET | CS-E1 | SP-ET | OF-ET | UG El O0.€€ C8-FT | SL-FI | 09-FI | OS-FT | OF-FT | S3-FT |] ST-FT | 00-FI | 06-1 | O8-ST | S9-ET | SG-ET | OF EL | O€-ET | OG-ET | GO-ET GSE GL-FL | O9-FT | OG-FT | OF-FT | S3-FI | ST-FT | 00-FT | 06-€1 | 08-€T | $9-ET | SS-€T | OF-ST | O€-ET | 0G-ET | G0-ET | C6-GL 0.3€ | 09-FI | OS FT | OF-FI | S-FI | ST-FT | 00-F1 || 06-8T | 08-ET | £9-ET | S¢-8T | OF-ET | OF-ET | 0-ET | 90-81 | 96-21 0-3 | g-TS OG-FL | OF- FI | CG-FL | ST-FI | 00-FT | 06-8T 08-81 | $9-€T | CG-€T | OF-ET | O8-ET | OG-EL | SO-ET | S6-ZT | O8-GI | OL-GT O.TE GE-FL | S-FI | ST-FL | 00-FT | 06-8T | SL-€T | 99-8I | ¢-8T pore 08-81 | ST-€1 | SO-€T | S6-2T | 08-41 | OL-GI | 89-61 g-O€ GB-FL | ST-FT | 00-FT | 06-8T | SL-ST | €9-ST | SC-ET | OF-8T | 0€-€T | CT-€T | CO-8T | $6-61 | OS-GT | OL-GT | S¢-GT | SF-aI 0.0€ | 9G |/pG]/e¢oc!|seo|ts _ og ‘ 6B | 8-1 | 2b (9% > GE|)PD FD @b| LD | OF : - | -AqIAnap optoadg ‘Wa | | “(paniwog\—"AIXXXNO ATAVL 419 USEFUL TABLES, ‘o1ndyg 4s91v9U OY} OI B.0 JO ‘9.0 ‘F.0 ‘LG CAO’ OINSY 4SaIvou OY] WOIZ CY.Q 49R1}GNS 8.0 JOE. “MOTOG BINSY ysoiveu oy} OF GO.Q UO ppv L.Q 10 F.Q st Aytavad ogtoeds oyy ur [uMOap oY JT ‘eg. UO ppv yy "que dod GQ.() IO ST-ST | GO-ST | $6-FT | O8-FT | OL-FT | 09-FT || SF FI | SE-FI | G-F1 OF | OO-FT | 06-€T | CL-ET | ¢9-E1 | S¢-€T | OF ST QTE CO-ST | 06-FT | O8-FT | OL-F1 | S¢-FT | CF FT 1 GE-PL | OG-FL | OFT “00-41 G8-€T | SL-EL | C9-€T | Of €T | OF-ET | O8-8T O-TE 06-FT | OS-FI | OL FL | So-FL | SF-FT | C&-FL |) OG-FL OL-FI | 00-F1 ESET CLET| COEL | 08-8 | OF-ET | OF- EL | SLET G.€e O8-FI | G9-FL | SS-F1 | SF FL] O€-FI | OG-FI || OL-FT | 96-€T | C8.) SLE | 09-€L | OG-€T | OF-ET | Co-€T | GLET | CO-81 0-.€€ G9-FT | S-FT | OF- FL | O€- FL | OG-FT | OL-FT || S6-ET | S8-ET | CL-€T | 09-€T | OS-E1 | OF-ET | CG-ET | ST-8T | SO-8T | 06-31 G.3E GG-PL | OF FL | O€-FL | O3-FI | CO-FT | S6-ET || $8-ST | OL-ET | 09-ET | OS-ET | SE-ET | G3-ST | ST-ET | 00-81 | 06-31 | 08-31 0. OF-FT | O€-FI | ST-FL | GO-FT | S6-€T | OS-€T || OL-ET | O9-ST CF-ET | SE-ET | CZ-ET | OL-ET | 00-1 | 06-21 | GL-31 | G9-31 G-I€ O€-FL | SIFT | GO-FT | S6-€T | O8-ET | OL-€T || 09-1 | FEL | CE-EL | SG-€T | OT-ST | 00-ET | 06-61 | SL-31 | $9-3T | S¢-3I OTE ST-PL | G0-F1 | 06-€L | OS-ET | OL-ST | SGT || CF-ST | SE-ST | OG-ET | OL-ST | 00-ET | €8-GT | SL-Z1 | 29-31 | OS-SL | OF- GI | g.0€ 00-FT | 06-ET | OS-ET | G9-ET | SS-ST | CF ET | OF-ET | OG-ET | OL-ET | 26-GT1 | GS-1 | GL-GI | €9-BI | OS-ZI | OF-ZI | OF-GI 0.0€ GS /PpS €9S)/6G9 |TS | OG | 67 | 8h 2b | 9D | SD | P| Sh | or | Lb | OF Ayaviy oyroods ‘wa ‘(panuyquog)—"AXXXO ATAVL 420 APPENDIX. TABLE CXXXVI.—For tHE CancuLaTIon oF THE ToTAL Soups or Sxim MILK FROM THE Fat AND SPECIFIC GRAVITY. For Use in the Dairy Laboratory. Fat. Specific Gravity. o1 02 0:3 o-4 o'5 o'6 o7 08 o-9 33°5 8°65 | 8°75 | 8°85 | 9:00 | 9:10] 9:25] 9°35] 9°45] 9-60 34°0 8°75 | 8°85 | 9°00 | 9:10 | 9:25] 9°35) 9°45] 9°60] 9°70 34°5 8°90 | 9:00 | 9°10 | 9:25 | 9°35] 9:50! 9°60} 9°70] 9°85 35'0 9°00 | 9°10 | 9°25 | 9:35 | 9°50} 9°60] 9°70} 9:85] 9°95 35'°5 9°10 | 9:25 | 9°35 | 9:50 | 9°60} 9°70} 9°85} 9:95] 10°10 36°0 9°25 | 9°35 | 9°50 | 9°60 | 9°70} 9°85} 9-95] 10°10] 10-20 36'5 9:35 | 9°50 | 9°60 | 9°70 | 9°85] 9:95 | 10°10 | 10°20} 10°30 37:0 9°50 | 9°60 | 9°75 | 9°85 | 9:95] 10°10 | 10:20 | 10°35 | 10-45 387'5 9°60 | 9°75 | 9°85 | 9-95 | 10°10] 10°20 | 10°35 | 10°45 | 10°55 , TABLE CXXXVII.—For tHe Conversion of THERMOMETRIC SCALES. For the Conversion of Degrees Fahrenheit into Degrees Centigrade. ‘Formula C=(F - 32) x 2 . Degrees Degrees Degrees Degrees Degrees Degrees Fahrenheit. | Centigrade. |; Fahrenheit.) Centigrade. || Fahrenheit. | Centigrade. 0 -17°78 51 10°56 78 25°56 5 — 15:00 52 Il‘1l 79 26°11 10 — 12-22 53 11°67 80 26°67 15 -9°44 54 12:22 90 aoe 20 — 6°67 55 12:78 100 37°78 25 -3°89 56 13°33 110 43°33 30 -1ll 57 13°89 120 48°89 31 - 0°56 58 14°44 130 54°44 32 0 59 15:00 140 60:00 33 0°56 60 15°56 150 65°55 34 11 61 16°11 160 7111 35 1:67 62 16°67 170 76°67 36 2:22 63 17:22 180 82:22 37 2°78 64 17°78 190 87°78 38 3°33 65 18°33 200 93°33 39 3°89 66 18°89 210 98°89 40 4°44 67 19°44 212 100°00 41 5:00 68 20°00 220 104°44 42 5:56 69 20°56 230 110-00 43 6-11 70 21:11 240 115-55 44 6°67 71 21°67 250 121-11 45 7°22 72 2222 260 126 °67 46 7:78 73 22°78 270 132°22 47 8°33 74 23°33 280 137°78 48 8°89 75 23°89 290 143°33 49 9°44 76 24°44 300 14889 50 10°00 77 25:00 TABLE CXXXVII.—(Continued). USEFUL TABLES. For the Conversion of Degrees Centigrade into Degrees Fahrenheit, Formula F=C x ° +32, os) Degrees Degrees Degrees Degrees Centigrade. Fahrenheit. Centigrade. Fahrenheit. -17°78 0 24 ja2 -15 5°00 oo 77:0 -10 14:00 30 86:0 -5 23°00 35 95 0 32:00 37°78 100°0 1 33°38 40-0 104°0 2 35°6 45 113-0 3 37°4 50 122-0 4 39°2 55 131-0 5 41:0 60 140°0 6 42°38 65 149°0 7 44°6 70 1580 8 46-4 75 1670 9 482 80 176-0 10 50°0 85 1850 1l 51°8 90 194°0 12 53°6 95 203-0 13 55°4 100 212-0 14 5g°2 105 2210 15 59-0 110 230°0 15°56 60°0 115 239'0 16 60'8 120 248-0 17 62°6 125 270 18 64:4 130 2660 19 66°2 135 275-0 20 68:0 140 254-0 21 69°8 145 ra) v2 716 150 302-0 23 73-4 DIFFERENCE TABLE. Degrees. F into C. | 1 0°56 18 ee Lal 36 3 l-67 ort 4 aie aes ay 278 9-0 6 3°33 10'S i 3°89 12°6 Ny 4-44 14-4 9 5:00 162 10 5°56 18-0 422 APPENDIX. TABLE CXXXVIII.—WetenHts anp MEASURES. Linear Measure. 1 inch . : . : a ; ‘ = 0°0254 metre. lfoot = 12 inches F i P : ; = 0°3048_ —,, lyard = 3 feet = 36 inches . : P . ‘ = 09144 ,, 1 metre = 10 decimetres = 100 centimetres = 1000 millimetres. 1 metre = 39°371 inches = 3°28] feet = 1-094 yards. Square Measure. 1 square inch 0-000645 sq. metre. 1 square foot = 144 square inches - 0-0929 +5 1 square yard = 9 square feet = 1296 sq. inches. = 0°8361 35 1 sq. metre = 100 sq. decimetres = 10,000 sq. centimetres = 1,000,000 sq, millimetres. 1 sq. metre = 1550°6 sq. inches = 10°764 sq. feet = 1196 sq. yards. Wt Cubic Measure. 1 cubic inch . : 3 = 0:00001639 cub. metre. 1 cubic foot = = 1728 cubic inches j = 0°0283 Ae l cubic yard = 27 cubic feet = 46,656 cubic ins. = 0°7645 =. 1 cubic metre = 1000 cubic decimetres = 1,000,000 cubic centimetres = 1,000,000,000 cubic millimetres. 1 cubic metre = 61,027 cub. ins. = 35°317 cubic ft. = 1°308 cubic yds. Measures of Capacity. 1 gill ; = 01420 litre. 1 pint = 4gills é = 05679 _ ,, 1 quart = 8gills= 2pints . = 1/1359 litres. 1 gallon = 32 gills = 8 pints = 4 quarts = 45435 —,, *] fern gallon = 68 oils = 17 pints = 84 quarts f = 96548 ,, 1 litre = 1000 cubic centimetres = 1,000,000 cubic millimetres. 1 litre = 7-043 gills = 1:7608 pints = 0 8804 quart = 0°2201 gallon = 0°1036 barn gallon.* Avoirdupois Weight. 1 grain . . é ‘ a = 0°0655 grammes. 1 drachm P . 3 ‘ j < 3 = 17718 ‘5 lounce = 16 drachms ? = 28°349 St l pound = 256 drachms = 16 ounces ‘ = 453°59 35 1 quarter = 7168 drachms = 448 ounces = 28 Ibs. = 12,7005 _,, 1 hundredweight = 28,672 drachms = a ozs. 112 Ibs. = 4 quarters . = 50°802 a 1 ton = 573,440 drachms = 35, 840 ozs. = 2240 Ibs. = 80 qrs. = 20cwt. . si : = 1,016,047 ,, 1 metric ton = 1000 Bionemues 1 kilogramme = 1000 grammes. 1 gramme = 10 decigrammes = 100 centigrammes = 1000 milligrammes. 1 gramme = 15°43 3 grains = = 0°5644 drachm = 0:03527 0z. = 0:002205 lb. = 0°00001968 cwt. = 0:000000984 ton. * The barn gallon is not a legal measure; all contracts made in barn gallons are null and void. It is, however, much used. USEFUL TABLES. 423 Useful Data. The gallon weighs 10 lbs. (of distilled water at 62° F.). The litre weighs 1000 grammes (of distilled water at 0° C.). 1 gallon = 44 litres approximately, lbarn gallon =10 ,, ” lkilogramme = 2} lbs. approximately. 1 hundredweight = 50 kilogrammes approximately. 1 cubic foot = 6°24 gallons. Note.— The metre and litre compared with the standard English measures are those defined by the Act of 1878, and are not the true metre and litre. The difference is due to the fact that the English measures refer to a temperature of 62°F., and the metric measures to a temperature of 0°C. In the Weights and Measures Act of 1878 the difference of temperature has not been allowed for. The following table shows the comparison between the two systems :— Metre. Litre. Kilogramme. | Inches. Gallon. Lbs. True values at 62°F., . ‘ 39°38203 0:22018 220462 Adopted in Act, . - 5 39 °37079 0-2200967 220462 TABLE CXXXIX.—Barn Gantons anp IMverntaL GALLoys. For the Conversion of Barn Gallons into Imperial Gallons. Barn Gallons. Imperial Gallons. Gallons. Pints. 1 Ses 2 1 2 45 4 7 3 6-375 6 3 4 ar 8 + 5 10625 10 5 6 12°75 12 6 7 14-875 lt 7 8 17-0 lj 0 9 Wh a ia! ti) 1 10 B25 os 2 For the Conversion of Imperial Gallons into Barn Gallons. Imperial Gallons. Barn Gallons. Imperial Gallons. Barn Gallons. | | 1 O47 | 10 | 4-70 2 0-94 1l 5:17 3 1-41 12 5-64 4 1-88 13 6:12 5 2°35 1 14 6:59 6 2-32 ; 15 7:06 i 3-2 ' 16 753 8 3-76 i 17 8-00 9 423 424 APPENDIX. TABLE CXL.—Taziz or Weicuts or Darry Propvcts. Milk at Farm. | Milk at Dairy.) Skim Milk. Des caad Thick Cream Lbs. Ozs. Lbs. Ozs. Lbs. Ozs. Lhs. Ozs. Lbs. Ozs. 1 pint, 1 43 1 48 1 42% 1 4 1 34 1 quart, 2 9 2 94 2 9% 2 8 2 1 gallon, 10 4 10 5 10 «6 10 0O 9 12 2 gallons 20 8 20 10 20 12 20 O 19 8 4% 30 12 30 15 31 2 30 (OO 29 «4 4 ,, 41 0 41 4 41 8 40 0 39 «(0 ae 51 4 51 9 51 14 50 0 48 12 6 61 8 61 14 62 4 60 0 58 «8 caer 71 12 72 3 72 10 70 0 68 4 8 ,, 82 (0 82 8 83 60 80 0 78 0 9 35 92 4 92 13 93 6 90 O 87 12 10° ,, 102. 8 103. 2 103 12 100 O 97 8 Lh 35 112 12 113° «7 114. 2 110 «=O 107. 4 12) 3, 123 0 123 12 124 8 120 0 117 0 13° 35 133 4 134 1 134 14 130 0 126 12 14, 143 8 144 6 145 4 140 0 136 8 15 Ca, 153 12 154 11 155 10 150 0 1446 «4 16a, 164 0 165 0 166 O 160 0O 156 0 Ve 45 174 4 175 5 176 «6 170 0 165 12 18 «Cy 184 8 185 10 186 12 180 0 175 8 19 ~=Cy, 194 12 195 15 197 2 1909 0 185 4 20 ~=«, 205 0 206 4 207. «8 200 0 195 0 DIFFERENCE TABLE. Lbs. Ozs. Lbs, zs. Lbs. Ozs. | Lbs. Ozs. | Lbs. Ozs. 1 pint, 1 43 1 48 1 42 1 4 1 33 1 quart, 2 9 2 94 2 9 2 8 2 7 3 pints, 3 134 3 132 3 144 3 12 3 103 2quarts, 5 2 5 2 5 3 5. (0 4 14 5 pints, 6 64 6 7% 6 72 6 4 6 14 3 quarts,,; 7 11 7 11g 7 12% 7 8 7 #5 7 pints, 8 15% 9 08 9 14 8 12 8 84 Note.—The milk at farm is assumed to be warm and freshly milked. The milk at dairy is assumed to be at the average temperature (60° F.) and a few hours old. Skim milk is assumed to be at the average temperature (60° F.). Butter cream is assumed to be at the average temperature (60°F.) and to contain 30 per cent. fat. Thick cream is assumed to be at the average temperature (60° F.) and to contain 50 per cent. fat. TABLE CXLI.—For THE CALCULATION OF THE WEIGHT OF BUTTER IN POUNDS OBTAINED BY CHURNING CREAM. cr ere er prea rae eee ey NS PETE NE re mr vena en EE ee ene Oe le creer rare Ven eT | Quarts oF CREAM CHURNED. Percentage of SSS Fat in Cream. | 1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90 | 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 15 044] 0-87 | 1:31 | 1:74 | 2-18 | 2°61 | 3°05 | 3:48} 3°92) 4:3: 8-7 | 13-1 | 17-4 | 218 | 26:1 | 30:5 | 34:8) 39-2] 43:5] 47:9] 52:2) 566) 60:9] 65:3] 696] 74:0) 78:3] 82°7| 87-0 16 0-47 | 0-93 | 1-40 | 1-86 | 2°33 | 2°69 | 2:16 | 3°72] 4:19] 4:65) 9:3 | 14:0 | 18°6 | 23:3 | 26-9 | 31°6 | 37°2 419] 46°5] 51:2] 55°83] 60:5] 65:1] 69°8| 73:4] 78:1] 83°7| 88-4; 93°0 17 0°50 | 0-99 | 1-49 | 1-98 | 2-48 | 2°98 | 3-47 | 3°97] 4:46] 4:96] 9:9 | 14:9 | 19°8 | 24°8 | 29°8 | 34-7 39-°7| 446] 496] 546] 59°] 64:5] 69-4] 74:4] 79-4] 84:3] 89:3] 94:2) 99-2 18 0°53) 1-05 | 1°58 | 2:10 | 2-63 | 3:16 | 3°68 | 4:21] 4:73] 5:26] 10°5 | 15°8 | 21:0 | 26:3 | 31°6 | 36°8 42°1| 47°3] 526) 57:9} 63:1] 68:4] 73°6| 78:9] 84:2] 89-4] 947] 99:9 105-2 19 0:56 | 1-11 | 1°67 | 2:23 | 2°79 | 3:34 | 3°90 4:46) 5°01) 5°57] 111 | 16:7 | 22°3 | 27°99 | 33-4 | 39:0 | 446] 501) 55-7] 613 66°8 | 72:4] 78:0] 83°6] 89:1] 94°7| 100-3] 105-8 L114 20 0°59 | 1:17 | 1:76 | 2°35 | 2°94 | 3°52 | 4:11 4°70 | 5°28] 5°87] 11:7 | 17°6 | 23-5 | 29:4 | 35-2 | 41-1 47:0, 52°8| 58°7| 64:6] 70°4] 76:3] 82:2] 8S°1} 93:9] 99:8] 105-7} 111°5 | 117-4 21 0°62 | 1-23 | 1°85 | 2-46 | 3-08 | 3°70 | 4:31 | 4:93] 5°54!) 6-16) 12°3 | 185 | 24-6 | 30°S | 370 | 43-1 49:3] 55:4] 61°6| 67:8] 73:9] 80:1} 86:2] 92-4] 98-6] 104-7] 110°9 | 117-0 | 123-2 22 0°65 | 1-29 | 1:94 | 2°58 | 3°23 | 3°87 | 4:52 5:16] 5°81) 6:45) 12-9 | 19-4 | 25-8 | 32:3 | 38-7 | 452 | 51-6! 58-1! 64:5] 71-0 77:-4| 83:9] 90°3] 96:8} 103-2] 109°7] 116-1 | i22°6 | 123°0 23 068 | 1-35 | 2-03 | 2°70 | 8:38 | 4:05 | 4:73 | 5-40} 6°08) 6°75| 13°5 | 20:3 | 27-0 | 33°8 | 405 47°3 | 54:0] 60°8; 67°5] 74:3] 81:0] 87°8] 94:5] 101:3| 108-0 | 114-8} 121-5] {28 | 135-0 24 0-70 | 1-41 | 2:21 | 2°82 | 3°52 | 4:22 | 4:93 | 563] 6:34] 7°04) 14-1 | 21-1 | 28-2 | 35-2 | 422 | 493 56°3| 63:4] 70-4] 77:4] 84:5] 91:5] 98-6] 105-6 | 1126 | 119-7 | 126 °7 | 183°3 | 140°8 26 073 | 1-47 2:20 | 2:93 | 3°67 | 4-40 | 513 | 5°86] 6°60 7°33 | 14:7 | 22-0 | 29-3 | 36-7 | 44-0 | 51-3 | 58-6} 66:0] 73:3] 806] 88-0] 95:3} 102-6} 110-0 | 117°3 | 124-6 | 131-9 | 159°3 1 146-6 26 0-761 1:52 | 2-29 | 3-05 | 3°81 | 4°57 | 5:33 | 6-10! 66] 7°62) 15-2 | 22-9 | 30-5 | 38-1 | 45-7 | 53-3 61:0! 686] 76:2] 83:8] 91:4] 99:1 | 106-7} 114°3 | 121-9 | 129°5 | 137.2] 144°8 | 152-4 27 0:79 | 1-58 | 2°37 | 3:16 | 3:96 | 4°75 | 5°54 | 6:33] 7:12) 7°91 | 188 | 23-7 | 31-6 | 39°6 | 475 554 | 63°3! 71:2] 79:1] 87:0} 94:9} 102-8 | 110-7 | 118-7 | 126°6 | 134°5 | 142-4} 150-3 | 158-2 28 0:82 | 1°64 | 2-46 | 3-28 | 4:10 | 4°91 | 5°73 | 6:55) 7°37] 819 16:4 | 24:6 | 32:8 | 41:0 | 49:1 | 57:3 | 65°5) 73:7] 81:9] 99:1} 98°3| 1065 114°7 | 122-9 | 131-0 | 139-2 | 147-4 | 155°6 | 163-8 29 0°S5 | 1-70 | 2°54 | 3°39 | 4:24 | 5-09 | 5-94 | 6°78 7:63 | 8:48] 17-0 | 25-4 | 33-9 | 42-4 | 50°9 | 59-4 | 67°S 76:°3| 84:8} 93:3} 101°8} 110-2] 118-7 | 127-2 | 135-7 | 144-2 | 152-6 | 161-1 | 169°6 30 0-88 | 1-75 | 2:63 | 3°51 | 4:38 | 5-26 | 6-14 | 7:02) 7°89] 8°77] 17°5 | 263 | 35-1 43-8 | 52°6 | 61-4 | 70:2] 78:9] 87°7]| 96:5 | 105-2 | 114-0 | 122°8 | 131°5 | 140°3 | 149-1 | 157-9 | 166-6 | 175-4 31 0-91 | 1°81 | 2°72 | 3°62 | 4°53 | 5-43 | 6°34 7-24} §15| 9°05| 18:1 | 27-2 | 36:2 | 45°3 | 54:3 | 63-4 72-4| 81:5] 90:5} 99°6 | 108-6 | 117-7 | 126°7 | 135°S | 144°8 | 153-9 | 162-9 | 172-0 | 181-0 32 0:93 | 1:87 | 2°80 | 3-74 | 4°67 | 5-60 | 654 | 7:47 8-41] 9:34) 18-7 | 28-0 | 37-4 | 467 | 56:0 | 65-4 74:7} 84:1] 93:4] 102-7] 112°] | 121-4 | 130-8 | 140-1 | 149°4 | 158-8 | 168-1 | 177-5 | 186-8 33 096 | 1-92 | 2°89 | 3-85 | 4:81 | 5-77 | 6:73 | 7°70] 8°66 9:62) 19-2 | 28-9 | 38-5 | 48:1 | 57-7 | 67°3 | 77:0] 86-6] 96-2 | 105-8 | 115-4 | 125-1 | 134-7 | 144-3 | 153-9 | 163-5 | 173-2 | 182°8 | 192-4 34 0-99 | 1-98 | 2:97 | 3-96 | 4:96 | 5-95 | 6-94 | 7:93] 8:92] 9°91} 19°8 | 29-7 | 39°6 | 496 59°5 | 69-4 | 79:3} 89:2} 99-1 | 109-0] 118-9 | 128-8 | 138°7 | 148°7 | 158°6 | 168°5 | 178-4 | 188-3 | 198-2 i 35 1-02 | 2:04 | 3°06 | 4:08 | 5-10 | 6:11 | 7°13 | 8°15 9:17| 10:19 | 20-4 | 30°6 | 40°8 | 51:0 | 61:1 | 71:3 | 81% 91-7 | 101-9 | 112:1 , 122°3 | 132-5 | 142-7 | 152-9 | 163-0 | 173-2 | 183-4 | 193°6 | 203°8 | 36 1:05 | 2:09 | 3:14 | 4:18 | 5:23 | 6-28 | 7:32 | 8°37 9:41 | 10-46} 20-9 | 31-4 | 41-8 | 52:3 | 62°8 | 73:2 | 83:7] 94:1 104°6 | 115°1 | 125-5 | 136-0 | 146-4 | 156-9 | 167°4 | 177-8 | 188-3 | 198°7 | 209-2 37 1-07 | 2:15 | 3°22 | 4°30 | 5°37 | 6-44 | 7°52 | 859] 9°67) 10°74 21°5 | 32-2 | 43-0 | 53:7 | 64:4 | 75-2 | 85-9] 96-7] 107-4 | 118-1 | 128°9 | 139-6 | 150-4 | 161-1 | 171-8 | 182°6 | 193-3 204°1 | 214°8 38 1:10 | 2:20 } 3:30 | 4:40 | 551 | 6°61 | 7771 8°81} 9°91 /11-01| 22-0 | 33-0 | 44:0 | 55:1 | 66:1 | 77:1 88:1} 99-1} 110-1 | 121°1 | 132°1 | 143+) | 154:1 | 165-2 | 176-2 | 187-2 | 198-2 | 209-2, 220-2 39 1-13 | 2-26 | 3:39 | 4:52 | 5-65 | 6-77 | 7-90 | 9°03} 10-16 | 11-29 22-6 | 33-9 | 45-2 | 56-5 | 67-7 | 79:0 | 90-3] 101-6 | 112-9 | 124-2 | 135-5 | 146-8 | 158-1 | 169-4 | 180°6 | 191-9 | 203-2 | 214°5 225°8 40 1-16 | 2°31 | 3:47 | 4:62 | 5°78 | 6-94 | 8-09 | 9°25] 10-40 | 11°56} 23-1 34-7 | 46-2 | 57-8 | 69-4 | 80-9 | 92-5} 104-0 | 115-6 | 127-2 | 138-7 | 150-3 | 161°8 | 1734 | 185-0 196°5 | 208-1 | 219°6 | 231-2 41 1-18 | 2°37 | 3°55 | 4-73 | 5-92 | 7-10 | 8-28 | 9°46] 10°65 | 11°S3 23-7 | 35°5 | 47-3 | 59-2 | 71°0 | 82-8 | 94-6] 106-5 | 118-3 | 130:1 | 142-0 | 153°8 | 165°6 177°5 | 189°3 | 201-1 | 212-9 | 224-8 | 236-6 42 1-21 | 2-42 | 3-63 | 4:84 | 6-05 | 7:25 | 8-46 | 9°67] 10°S8 | 12°09) 24:2 | 36:3 48-4 | 60°5 | 72°5 | 84:6 | 96-7 | 108-8 | 120-9 | 133-0 | 145-1 | 157-2 | 169°3 | 181-4 | 193-4 | 205-5 | 217° | 229-7 | 241°8 43 1-24 | 2-47 | 3-71 | 4:94 | 6-18 | 7-42 | 8°65 | 9°89] 11:12] 12°36 | 24°7 37-1 | 49-4 | 61-8 | 74:2 | 86°5 | 98-9] 111-2 | 123-6 | 136-0 | 148-3 | 160-7 | 173°0 | 185-4 197-8 | 210°1 | 222°5 | 234°8 | 247-2 44 1-26 | 2°52 | 3°79 | 5-05 | 6-31 | 7°57 | 8°83 | 10°10) 11°36 | 12°62) 25-2 37-9 | 50:5 | 63-1 | 75-7 | 88°3 | 101-0 | 113-6 | 126-2 | 138-8 | 151-4 | 164:1 176°7 | 189°3 | 201°9 | 214°5 | 227-2 | 239°8 | 252-4 45 1-29 | 2-58 | 3-87 | 5:16 | 6-45 | 7°73 | 9-02 | 10-31 | 11-60 | 12°89 | 25°8 38-7 | 51°6 | 64-5 | 77°3 | 90-2 | 108-1 | 116-0 | 128-9 | 141°8 | 154-7 | 167°6 180°5 | 193-4 | 206-2 | 219-1 | 232°0 | 244-9 | 257°8 46 1-32 | 2°63 | 3-95 | 5-26 | 6°58 | 7°89 | 9-21 | 10°52] 11°84] 13°15 | 263 39°5 | 52-6 | 65°8 | 78-9 | 92-1 | 105-2] 118-4] 131-5 | 144-7 | 157°S | 171-0 | 184-1 | 197°3 210-4 | 223°6 | 236°7 | 249-9 | 263:0 47 1:34 | 2-68 | 4:02 | 5°36 | 6°70 | 8-04 | 9°38 | 10°72 | 12°06 13-40 | 26-8 | 40-2 | 53°6 | 67-0 | 80-4 | 93:8 | 107-2] 120-6: 134-0 | 147-4 | 160°8 | 174-2 | 187°6 201-0 | 214°4 | 227-8 | 241°2 | 254°6 | 268-0 48 1:36 | 2-73 | 4:09 | 5-46 | 6°82 | 8:18 | 9°55 | 10°91 | 12-28 | 13°64 27-3 | 40-9 | 54-6 | 68-2 | 81-8 | 95-5 | 109-1 | 122°8 | 136-4 | 150-0 | 163-7 | 177°3 191:0 | 204°6 | 218-2 | 231°9 | 245°5 | 259-2 | 272°8 49 1:39 | 2-77 | 4:16 | 5-55 | 6-94 | 8-32 | 9-71 | 11°10] 12°48 13-87 | 27°7 | 41:6 | 55-5 | 69-4 | 83-2 | 97-1 | 111-0 | 124-8 | 138-7 | 152-6 | 166-4 180°3 | 194-2 | 208°1 | 221-9 | 235-8 | 249-7 | 263°5 | 277-4 60 1-41 | 282 | 4-23 | 5-64 | 7-05 | 8-46 | 9-87 | 11-28 | 12°69 14:10 | 28-2 | 42:3 | 56-4 | 70°5 | 84-6 | 98-7 | 112-8 | 126-9 | 141°0 | 155-1 | 169-2 | 183°3 | 197-4 211°5 | 225°6 239-7 | 253-8 267°9 | 282°0 See ree eR SOE SRE eee ees eee eer ee ee 425 INDEX. A Abbe refractometer, 347. Abnormal milks, 153, 154. Acetic acid and acetates, 8, 31, 48. Estimation, 142, 144. Solubility of butter fat in, 332. Acetyl derivatives of milk-sugar, 17. Acidity, Determination of, 133. Development of, 135, 179, 277. due to lactic acid, 17. Estimation of, in commercial milk- sugar, 386. Acids, Fatty (see also Soluble and insoluble fatty acids), 1, 50-56. Volatile, Estimation of, in sour milk, 142-145. Acrolein, 48, 49. Adamkiewicz’ reaction, 21. Adenin, 24. Adulteration of butter, 353. Cheese, 383. Commercial milk sugar, 386. Cream, 266, 273. Milk, 173-189. Alanine, 23, 25. Albumin (see also Lactalbumin), 7, 27, 28, 37. Action of heat on, 193, 196, 197. Composition, 37. Estimation, 129-132. Heat of combustion, 406. in colostrum, 161. in gamoose milk, 400. Preparation, 37. Properties, 37. Albumins, 20. Albuminoid ammonia, 285. Albumose and peptone nitrogen in cheese, Estimation, 377, 382. Albumoses, 27. Alcohol, Estimation, 141. in milk, 41. . Micro-organisms producing, 280, to = for] Alcohol, Use of, for preserving milk samples, 189. Alcoholic extract in cheese, 380. Fermentation, 7, 280. Aldehyde figure, 136. - reactions of proteins, 21. Alkalies, Estimation, 83. Alkalinity of soluble ash, Estimation, 82 Alteration of specific gravity by change of temperature, 74. Amino-acids, 19, 22-26. -compounds in cheese, Estimation, 377, 382. Ammonia, Free and albuminoid, 285. ' -free water, 287. in cheese, Estimation, 376, 381, 382. in milk, Estimation, 141. Nitrogen, 26. Amphoteric reaction, 9. Amy] alcohol, for fat estimation, 138. for milk testing, 225, 235. Anabolic ratio, 407. Analytical problems, 244-253. Annatto, 176. Appeal to the cow, 170. Aqueous extract of cheese, Esti- mation, 375, 380. Arachis oil, 345. Arginine, 23. Argonine, 388. Artificial human milk, 407. 55 thickening of cream, 273. Asbestos for milk analysis, 77, 120. Ash, 39, 153. Composition, 40. Density of, in milk, 73. Estimation, 81. in commercial milk-sugar, 386. in cream, 138. Insoluble, 39. of cheese, Estimation, 374, 376, 380. of human milk, Composition, 397. 426 Ash, Soluble, 39. Variations of, in milk, 153. Aspartic acid, 23. Ass, Milk of, 392, 404. Automatic burette, 223. Avé-Lallemant, Method of, 325. Ayrshire cows, 157-158. B Bact.ut, 275. Bacteria, 275, 276. Bacteriological examination of water, 291. Bellelay cheese, 371. Benzoic acid, 178. _ Estimation, 184. Bichromate, Potassium, for preserv- ing milk samples, 190. Biological and sanitary matters, 275- 300. Birotation, 12. Ratio, Estimation, 385. Bitch, Milk of, 392. Bitter milk, 281. Biuret reaction, 20. Blood, detection, 177. in milk, 281. Blue milk, 280. Bondon cheese, 365, 367. Boric acid, 178, 183. Detection, 83, 183, 311. Estimation, 84-88, 312. Brains, Adulteration with, 174. Brie cheese, 365, 367, 371. Bromhydrins, 49. Bromine absorption, 334. Buffalo, Milk of, 392, 397. Bulgarian sour milk, 300. Burette, Automatic, 223. Burettes, Standardisation, 412. Butter, 301-357. ¢ Action of salt, 304. Analysis of, 308-314. Composition, 301-304. -fat analysis, 314-357. Density, 45, 342-345. Detection of adulteration, 353. Microscopical examination, 338-342. Physical examination, 338-352. Testing, 228, 238, 239, Butter milk, 357-361. Analysis, 147, 360. Testing, 225, 235. INDEX. Butyric acid, 42. Estimation in milk, 144. : Micro-organisms producing, 276, 279. Butyro-refractometer, 343. Byre test, 170. Cc Cacto-CavaLLo (cheese), 366, 368. Calcium, Estimation, 82. Camel, Milk of, 392. Camembert cheese, 365, 367, 371, 379. Cane sugar— Adulteration by, 174. Detection, 105. Estimation, 101-105, 387. Heat of combustion, 406. in condensed milk, 174. Cans, Sample, 210. Cantal cheese, 381. Capric acid, 42. Caproic acid, 42. Caprylic acid, 42. Caraway cheese, 366. Carbon dioxide, 41. Estimation, 147. Casein, 7, 20, 26, 28-36, 387-389. Action of rennet, 28, 34, 364. Analysis, 388. B-, 39. Behaviour with lime salts, 30. Composition, 29, 30, 32. Estimation, 129-132, 311, 389. Genuine, 30. Heat of combustion, 406. in colostrum, 130. of gamoose milk, 399. Preparation, 33. Products of hydrolysis, 33. Reactions, 28. Rotatory power, 32. State of, in milk, 8. Caseinogen, 27. Caseoses, 33-36. Cat, Milk of, 392. Cheddar cheese, 366, 368. Cheese, 365-384. Adulteration, 383. Analysis, 373-384. Classification, 365. Composition, 366-372. Hard, 366, 368. Heavy metals in, 372. Moulds in, 372. INDEX. 427 Cheese, Preparation, 365. Proteins, 369. Ripening, 372. Soft, 365, 367. Sour milk, 366. Testing, 228, 238. Cheese-making, Control of, 384. Chemical analysis of water, 284-291. Control of cheese-making, 384. Churning, 359. Separating, 260. the dairy, 207-274. Chemist, dairy, Duties of, 207. Cheshire cheese, 366, 368. Chlorhydrin, 49. Chlorides, 8. Estimation, 82, 285, 310, 374, 376, 380. Chloroform, for preserving milk samples, 189. Cholera, 283. Chocolate, Milk, 389. Cholesteryl, 43, 49, 119, 329. Choline, 41. Chromogenic organism, 280. Chromo-proteins, 20. Chrysotile for milk analysis, 78, 120. Churning, Control of, 359. of butter, 305-308. Citric acid, 8, 31, 40. Estimation, 88. in gamoose milk, 398, 400. in human milk, 397. Inversion of cane sugar by, 102. Cladothrix, 275. Clotted cream, 269. Cocoa, Milk, 389. Coco-nut oil— Detection, 319, 322, 323, 345, 353. Cold, Action of, on milk, 203-206. storage for milk samples, 191. Coli communis, B., Detection, 294. Colostrum, 161-164. Human, 393. Colour of milk, 9. water, 285. test, Specific, for butter adulter- ants, 330. Colouring matter of milk, 41. of milk, Artificial, 176. Detection, 294. Commercial milk-sugar, 385. Composition, General, of milk, 1-9. Condensed mare’s milk, 404. milk, 198-201. Analysis, 139. Testing, 237, Contamination of milk, 283. Control of cheese-making, 384. Churning, 359. the dairy, 207-274. Milk during delivery, 242. Separators, 260. Copper-zinc couple, 288. Corps granuleux, 162. Cotton-seed oil, 330, 345. Cow, Appeal to the, 170. Milk of, 1, 150. Cow’s milk, Koumiss, 297. Cream, 264-275. Analysis, 137. Artificial thickening, 273. Ash, 267. -cheese, 367. Clotted, 269. Composition, 264-267. Density, 268. Estimation of fat from total solids, 138. Froth, 269. Homogenised, 273. Preservatives in, 182, 183. Rising of, 167, 194, 251. Standards for, 266. Testing, 227, 237. Thickness of, 270. Crescenza cheese, 371. Critical temperature, 331. Curd, 362, 363. Estimation, 132, 311. Curdled milk, Ash of, 40. Determination of cause of, 250. Curdling, micro-organisms, 276, 279, 280. Cystine, 24, D Daity variations, 159. Dairy, Chemical control of, 207-274. Chemist, duties, 207. Shorthorns, 155-158. Decomposed milk, Analysis, 139-148. Decomposition of fat, 57, 354. milk, 275-282. Dehydrolactic acid, 17. Densimetric method of fat estima- tion, 103. Density (see also Specific gravity)— Alteration of, by change of tem- perature, 74. Determination of, 60-61, 213-218. Modes of expression, 58. 428 Density of butter fat, 45, 342-345. of cream, 268. of water, 58. Derby cheese, 366. Deutero-proteoses, 22, 33, 34, 36. Devon cows, 158. Devonshire cream, 269, Dextrin, Adulteration by, 174. Dextrose (see Glucose). Diabetic milk, 408. Diamino-acids, 23, 26. Diazo reactions, 21. Dichlorophenol for preserving milk samples, 190. Digestible proteins, Estimation, 377, 378. Diluted condensed milk— Composition, 200. Detection in milk, 195. Dilution of cream, 271. Diphtheria, 283. Diplococci, 275. Disease, Conveyance of, 282-284. Drying apparatus, 79. Dulcitol, 15. Dunlop cheese, 366. Dutch cheese, 366, 369, 371. Cows, 157, 158. Dys-caseose, 33, 34, 35. E Epam cheese, 366, 369, 371. Elaidic acid, 55. Elephant, Milk of, 392. Emmenthal cheese, 366, 368, 370, 371. Energy surface, 5. Enzymes, 8, 15, 18, 23, 27. Detection, 195, 196. Ripening of cheese by, 373. Equivalent, Saponification, 324. Ether, for fat estimation, 111. for preserving samples, 190. Eucasin, 388. Evening milk, Morning and, 159. Ewe, Milk of, 392, 402. Extract, Alcoholic, 380. Aqueous, 375, 380. F Fat (see also Butter fat), 1-7, 41-47. Adulteration of cheese with foreign, 383. INDEX. Fat, Composition, 42. Density, 45-47, 67, 68, 73. Difference between butter fat and other, 315. Estimation— by measurement of cream, 122. Centrifugal, 221-242. Densimetric, 123. Gravimetric, 107-122. in butter, 228, 238. in cheese, 228, 238. in cream, 137, 138, 227, 237. in milk powders, 149. Indirect, 122-124. Optical, 123. Volumetric, 122, 221-242. Heat of combustion, 46, 406. ot different animals, 390, 391. Refractive index, 46. Determination, 345. Size of globules, 41, 390. Variations of, in milk, 150-152, 154-161. Fatty acids, 1, 42, 50-56. Feeding, Influence of, on the com- position of milk, 170. Fehling’s solution, Estimation of milk-sugar by, 95-100. Fermentation, Alcoholic, 7, 280. Butyric, 279. Lactic, 17, 279. Test for milk, 385. Fermented milk, Analysis, 139-148. Flasks, Standardisation, 413. Fluoboric acid as preservative, 178. Fluorides and fluosilicates as pre- servatives, 178. Detection, 185. for preserving milk samples, 190. Foot and mouth disease, 283. Fore milk, 160. Formaldehyde (formalin) as a pre- servative, 178. Detection, 186-188. for preserving milk samples, 190. Free ammonia, 285. Fresh butter, 301-304, 313. Froth of cream, 269. Frozen milk, 203-206. G GALACTIN, 27. Galactinic acid, 14. Galactose, 18. Galacto-zymase, 27. INDEX. Gamoose, Milk of, 398-402. Gases of milk, 41. Gelatine, Detection of, 273. Nutrient, 291. Gerber method, 228-240. German cows, Milk of, 158. Gervais cheese, 365, 367, 379, 383. Glarner cheese, 366. Globules of fat, 1-7, 41, 305, 390. Rising of, 255-258. Size of, 41, 390. Surface energy, 5. of water in butter, 306. Globulin, 20, 27, 28, 38. in colostrum, 162. Globulins, 20. Glyceric acid, 48. Glucosamine, 25. Glucose, 16. Gluco-proteins, 20. Glutamic acid, 23, 25. Glycerides, 1, 42, 315. Glycerine, Adultcration by, 174. Glycerol, 42, 47. Glycero-phosphate, Estimation, 389. Glycine, 23, 25. Glycolic acid, 48. Glyoxaline, 24. Glyoxylic acid, 48. Goat, Milk of, 392, 403. Cheese from, 366. Gorgonzola cheese, 366, 370, 371. Grana cheese, 369, 370, 371. Green milk, 281. Gruyére cheese, 366, 368, 370, S71. Guanine, 24. Guernsey cows, 157, 158. H Havocey, reaction of proteins, 21. Hardness of water. 289. High specific gravity, Determination of cause of, 246. Histidine, 23, Histones, 20. Holstein cows, 157. Homogenised cream, 273. milk, 137, 274. Human colostrum, 393. milk, 200, 392-397. Humanised milk, 407. Hydrofluoric acid, for preserving : milk samples, 190. Hyphomycetes, 275 Hypo-xanthine, 25, 41. 42 I Ignition, Loss on, 285. Indigestible nitrogenous substance, Estimation, 377. Indirect estimation of fat, 122-124. Insoluble ash, 39. Estimation, 81. Fatty acids, 42. Estimation, 326. Invertase, 15. Estimation of cane sugar by, 103,. 387. Iodine absorption, 333. J JERSEY cows, Milk of, 155-158. Junkets, 387. Kepuir, 299. Analysis, 147. Kerry cows, Milk of, 155-158. Kjeldahl’s method for nitrogen estimation, 124. Koumiss, 297, 400, Analysis, 147. Kyrins, 22. L LactaLBum in, 7, 27, 28, 37. Estimation, 129-132 Lactase, 15. Lactic acid, 17, 18. Estimation, 133. Lactic fermentation, 17, 279. Lactide, 17. Lactobionic acid, 10, 14. Lactoform, 388. Lacto-globulin, 20, 27, 28. 38. Lactometers, 62, 213-218. Standardisation, 414. Lacto-protein, 27. Estimation, 130. Lactoscope, 123. Lactose (see Milk-sugar). Lacto-somatose, 388. Lauric acid, 42. 52. Lecithin, 41, 43, 119. Estimation, 137. in colostrum, 162. 430 INDEX. Leffmann-Beam method, 221-228. Milk— Leicester cheese, 366. Action of cold, 203. Leucine, 23, 25. heat, 191. Leuconostoc, 275. Liebermann’s reaction, 21. Limburg cheese, 383. Lime (see Calcium). Lime-water, 133. Limits and standards, 164. Linolenic acid, 56. Linolic acid, 55. Llama, Milk of, 392. Loss on ignition, 285. Low specific gravity, Determination of cause of, 244. Lysine, 23. M Maanesium estimation, 82. Majorcan cheese, 370. Mammary tissue, Adulteration by, 174. Mannitol, 15. Mare, Milk of, 392, 403. Mare’s milk, Koumiss, 297. Margarine, detection, 319. Properties, 316, 319. Maumené figure, 336. Mazoum, 300. Organisms from, 289, 300. M‘Conkey’s media, 292. Melanine, 26. Membran-slim, 2, 38. Membrane, Mucoid, 2-4. Mercuric nitrate, Wiley’s, 90. Mercury salts for preserving milk samples, 190. Metabolic ratio, 407. Metals, Heavy, in cheese, 372. Meta-phenylene-diamine, 191, 288. Meta-phosphoric acid, 95. Meta-proteins, 22. Micrococci, 275. Micro-organisms, 275-282. Action of, on milk, and milk-sugar, 17, 276. Destruction by heat, 192. in cheese, 372. in separated milk, 262, 278. in separator slime, 261. Products of, 297-300. “Microscopical examination— of butter, 338-342. of milk, 177, 253, 254. 195, micro-organisms, 275-282. rennet, 6, 362. as a food and a medicine, 405. Bitter, 281. Blue, 280. Classification, 390. -cocoa and -chocolate, 389. Constituents of, 1-57. Conveyance of disease by, 282. during delivery, Control of, 242. General composition, 1-9. Green, 281. Growth of bacteria in. 276. Homogenised, 274. of mammals other than the cow, 390-405. out of condition, 281. Powders, 201; analysis, 149. Products of micro-organisms from, 297-300. Red, 281. Ropy, 281. Soapy, 282. Tuberculosis in, 282. Violet, 281. -wine, 389. Yellow, 281. Milk scale, 69, 75. Milk-sugar, 1, 7, 9-16. Acetyl derivatives, 15, 401. Birotation, 12, 386. Commercial, 385-387. Density, 11, 13, 73. Estimation by alcohol, 90. by Fehling’s solution, 95-100, by Pavy’s solution, 100. Polarimetric, 90-95. Fermentation, 17, 279, 280. Heat of combustion, 406. Micro-organisms acting on, 276. Modifications, 10-13. Multi-rotation, 10, 11. Oxidation, 10, 14. Preparation, 15, 16. Products derived from, 17. Reactions, 10, 14, 15. Rotatory power, 10-13, 93, 193. Milkers, Conveyance of disease by, 283. Millon’s reaction, 21. Mineral analysis, 82-84. Constituents, 1, 39. (see also Ash). Mono-amino acids, 23, 26. INDEX. Montgomery cows, Milk of, 157. Monthly variations, 158. Morning and evening milk, 159. Moulds, 275, 282, 372. Mucic acid, 14. Mucoid protein, 2, 8, 20, 38. Mule, Milk of, 392. Multiple standard, 167. Multi-rotation, 10, 11. Myristic acid, 42, 52. N NaPuTHoL, #-, 178. Detection, 185. Nessler solution, 287. NeufchAtel cheese, 365, 367. Nitric acid nitrates, 287, 311. Nitrites, 288. Nitrogen— Amidic, estimation, 377, 382. Albumose, estimation, 377, 382. Estimation, 124. Peptone, estimation, 378, 382. Protein, estimation, 378, 382. Nitrogenous substance, Indigestible, Estimation, 377. Norfolk cows (red-polled), 155-158. North Devon cows, 158. Nuclein, 28. in colostrum, 161. Nucleo-proteins, 20. Nutrient media, 291-293. Nutritive ratio, 407. Nutrose, 388. Oo OueEtIc acid, 42, 54. Oleo-refractometer, 345. Ornithin, 23. Ortol, 23. Osones and osazones, 10, 15. Ovens, Water, 79. Oxalic acid, 14, 31, 48. Oxygen absorbed, Estimation, 288. Oxyproline, 2+. P Pauwitic acid, 42, 53. Palm nut oil, 325, 345. Para-phenylene diamine, 191, 199. Parmesan cheese, 366, 371. 431 Partial milking, 160. Pasteurised milk, 192, 193, 197. Growth of organisms in, 276. Pathogenic organisms, 276, 282. Pavy’s solution, 100. Pecto-galactinic acid, 14. Pedigree, shorthorns, Milk of, 155- 158. Pepsin, 20, 33. Peptides, 22. Peptones, 22. in cheese, 378, 382. in colostrum, 162. Test for, 378. Peptonised milk, 408. Phenylalanine, 24. Phosphates, 30, 38, 40. Phosphoric acid, 31. Estimation, 82. Phospho-proteins, 20. Pickled butter, 305, 313. Pipettes, Standardisation, 413. Placentine cheese, 370. Pleuro-pneumonia, 283. Polarised light, Microscopical exami- nation of butter under, 338- 34. Polenske process, 314. Polypeptides, 19, 22. Pont I’ Evéque cheese, 360. Poor milk. Determination of cause of, 248. Porpoise, Milk of, 392 Port du Salut cheese, 366, 371. Potash absorption, 324 Potassium, Estimation, 83. Powders, Milk, 141, 201. Preservation of milk samples, 189. Preservatives, 177-189. in butter, 308, 311-313. Detection, 183-189, 311-313. Problems, Solution of, 244-253. Process, Reichert, 316. Proline, 24. Propionic acid, Estimation, 144. Proteins, 1-7. 18-39. Analysis, 23, 26. Classification, 20. Density, 73. Estimation, 124-133, 136. Heat of combustion, 406. Hydrolysis, 22-26. 33-35. in butter, 2, 301, 305. in sour milk, Estimation, 140. Micro-organisms acting on, 276. Mucoid, 20, 38. of cheese, 375-382. 432 Proteins of colostrum, 161. of human milk, 397, of milk, 20, 26-39. of milk of different mammals, 391. of whey, 34, 363. Properties, 18-20. Reactions, 20. Proteoses, 22. in colostrum, 162. Proximate analysis of butter, 308. Purine, 24. Pyrimidine, 24, 25. R Rassit, Milk of, 392. Rancidity, 57, 357. Reaction of milk, 9. Specific temperature, 336. Recknagel’s phenomenon, 75. Red-polled cows, Milk of, 155-157. Refractive index, 46. Estimation, 345-351. Refractometer, Abbé, 347. Butyro-, 343. Oleo-, 345. Reichert process, 316. Relative Molecular Maumené figure, 337. Rennet, 22, 27, 28, 364. Action of, 34. Detection, 174. Preparation, 364. Testing, 365. Ripening of cheese, 372. Rise of specific gravity of milk, 75. Rising of cream— Change of composition on, 167- 169. Explanation of, 255-258. in sterilised milk, 194-195. Precautions against, 169. of fat globules, 255-259. Romadur cheese, 383. Ropy milk, 253, 281. Roquefort cheese, 366, 369, 372. Ss SACCHAROMYCETES, 275. Salers cheese, 381. Salicylic acid, 178. Detection, 184. for preserving milk samples, 190. INDEX, Salt, Action on butter, 304. Butter, 301-304, 313. Estimation, 310, 360, 374, 376, 380. Salts of casein, 7, 30. of milk, 8, 39-41. Sample cans, 210. Samples, Preservation of, 189. Sampling of butter, 309. Milk, 208. Water, 284, 291. Sanitary precautions, 295. Sanose, 388. Saponification, 43. Equivalent, Estimation, 324. Sarcine, 275. Sarcolactic acid, 17. Scale for specific gravity correction for temperatures, 75, Milk-, 69. Scarlatina and scarlet fever, 283. Schizomycetes, 275. Sclero-proteins, 20. Seasonal variations, 158. Sediment in milk, 253. Separated milk, 253-262. Analysis, 139. Detection in milk, 175. Testing, 225, 235. Separators, 257-259, Control of, 260. Separator slime, 261. Serine, 23, 25. Sesamé oil, 330, 345. . Sheep, Milk of, 392, 402. Cheese from, 366. Shorthorns, Milk of, 155-158. Skim milk (see Separated milk). Slim-membran, 2. Slime, Separator, 261. Smell of water, 235. unusual, Determination of cause of, 249. Soapy milk, 282. Sodium, Estimation, 83. Solids not fat, 150-152. Density, 68, 73. Estimation, 114, 120. in butter, 310. in sour milk, 144. Limits, 150, 164, 165, 167. Soluble extract, Estimation, 375. Fatty acids, Estimation, 326. Sour milk, Analysis of, 139-148. Bulgarian, 300. Cheese, 366. Determination of cause of, 250. _ INDEX. 433 Souring of milk, 135, 179, 277. T Sow, Milk of, 392. Specific gravity, 58-76, 213-218. TaBLes, Appendix, 415-424, Change of, with temperature, Tartronic acid, 48. 74. Taste, Butter, 281. Estimation, 60-63, 140, 213-218. Sweet, 247. High, Determination of cause of,| Unusual, 249. 246. Terpenes, for preserving milk Low, Determination of cause of, samples, 190. 244. Testing of milk and milk products, of colostrum, 162. 210, 213-242. of milk, 58-76. Tewfikose, 7. Relation between, and fat in| Theory of churning, 305. cream, 267. Separators, 256. Rise of, on standing, 75. Thermolactometers, 213. Variations, 63. Thermometers, Standardisation of, Specific temperature reaction, 336. 414. Specific volume, 71, 345. Thick butter, 305, 314. Spirilla, 275. Thick milk, Determination of cause Sporogenes enteritidis, B., 295. of, 252: Sprengel tube, 60. Thickening of cream, 273. Stall test, 170. Thymol, for preserving milk samples, Standardisation of apparatus, 410- 100, 414, Total nitrowen, Estimation, 124. Standards for ash and chlorine, ; Total solids, Density, 65, 71. 167. Estimation, 76-81, 218-221. Cream, 267. in cream, 138. Fat, 164-167. in water, 285 Solids not fat, 164-167. Soluble extract, 375. Total nitrogen, 167. Trypsin, 34. Water in butter, 313. Try ptophane, 24. Staphylococci, 275. Tuberculosis, 276, 282. Starch detection, 106, 174. Typhoid, 283 Estimation, 106. Tyrosine, 24, 26. Starters, 361. in colostrum, 167. Stoaric acid, 42, 53, 54, 56. Tyrothrix, 373. Sterilisation, for preserving milk samples, 190. Sterilised milk, 192-197. : U Analysis of, 137. Detection in milk, 195. _ UNSWEETENED condensed milk, 199. Preparation, 192. ) Detection, 195. Stilton cheese, 366, 368. Unusual taste of milk, Determination Stracchino cheese, 365, 367. of cause of, 249. Streptococci, 275. Urea, 8, 41. Strippings, 160. in colostrum, 162. Sugar, see Caue- and Mi/k-sugar. Yield from proteins, 406. Sulphites, as preservatives, 179, 312. Sulphuric acid, Estimation, 83. Vv Estimation of strencth, 224. o Supply, Water, 284-295. | VALINE, 23. Sussex cows, Milk of, 157. Vegetable oils, Tests for, 330. Sweet taste, Determination of cause, Violet milk, 281. 247. _ Viseogen, 273. Sweetened condensed milk, 19S. Viscosity of butter fat, 351. Syntonin, 28 _ Cream, 270-274. 2: ye) 434 Viscosity of Fatty acids, 54. Milk, 9. Volatile acids, Estimation, 142-145, Fatty acids, Estimation, 316-324. Volumetric method for the estimation of milk-sugar, 99-101. of fat, 122, 221-242, Ww Water, Adulteration with, 173. of butter with, 313. Analysis, 284-295. Bath, 81, 219. Boiling points of, 415. Conveyance of disease by, 283. Density, 58. Detection of added, 173, 244. Estimation, in butter, 309. in cheese, 374, 376, 380, 382. in milk, 78. in butter, 302-304. in butter-milk, 360. Oven, 79. Supply, 284-295. INDEX. Weights and measures, 422, 423. of dairy products, 424. Standardisation of, 410. Welsh cows, Milk of, 157, 158. Wensleydale cheese, 366. Westphal balance, 60. Whale, Milk of, 392. Whey, 362. Analysis, 147. Proteins of, 34, 363. Testing of, 225, 235. Wine, Milk-, 389. Woman, Milk of, 200. x XANTHINE, 24. Xanthoprotein reaction, 20. ¥. Yuast, Pink, 281. Yeasts, 275. Yellow milk, 281. York cheese, 369. BELL AND BAIN, LIMITED, PRINTERS, GLASGOW CHARLES GRIFFIN & COMPA = BG Ow 7, LIMITED. \ NY, WZ Sir A SUMMARISED LIST OF THE ENGINEERING, MINING, METALLURGICAL AND TECHNICAL PUBLICATIONS i Charles Sriffin § Co., Limited. A Turse Publications may be obtained through any Bookseller in the United Kingdom, or will be sent on receipt of a remittance to cover published price and postage. To prevent delay, Orders should be accompanied by a Cheque or Postal Order crossed ‘‘Untox of Lonpon anp SmituH’s Bank, Chancery Lane Branch.” Telegrams— 3634 Gerrard. L. O N D O N: ‘*Explanatus,” London. Telephone— hae 1-3-xvi. I2 EXETER STREET, STRAND. WD W 7 GRIFFIN’S ENGINEERING PUBLICATIONS. THE DESIGN OF EAMG GIRDERS, AND COLUMNS in Machines and Structures. By W. H. ATHERTON, 6s 0d Beet CONSTRUCTION (Practical Treatise on). By Prof. C. FIDLER, fie 8 M.Inst.C.E. FourtH EpItTion, Revised, - a _ 0s ) REINFORCED CONCRETE (Principles and Design). By R. ae CouLs CONSTRUCTIONAL STEELWORK. By A. w. FARNSWORTH, - + =net. 108 6d DOCK ENGINEERING, By Brysson CUNNINGHAM. SECOND EDITION. aut sida Folding Plates and other Illustrations, - - a a 30s HARBOUR ENGINEERING. By BRYSSON CUNNINGHAM. In Large 8vo. te) : P Profusely Illustrated, - 7 - net. 16s 0 DOCK AND HARBOUR’ ENGINEER'S REFERENCE BOOK. In Pocket Size, Leather. Fully Illustrated. By BRYSSON CUNNINGHAM. - Boe -net. 7s 6d HYDROGRAPHIC SURVEYING. By Commander 8S. Mrssum, R. N., - net. 12s 0d COAST EROSION AND PROTECTION. By E. R. MarrHEws, - - net. 10s 6d THE CONSTRUCTION OF DAMS. By Prof. E. R. MATTHEWS, - At Press, HYDRAULIC POWER AND HYDRAULIC MACHINERY. By Prof. B. RosBINnson, M.Inst.C.E. THIRD EDITION, Revised, — - net. 253 0d MODERN PUMPING AND HYDRAULIC MACHINERY. By E. BUTLER, net. 188 0d PUMPING MACHINERY (Steam and Water Pressure). By HENRY DaveY, M.Inst.C.E, SECOND EDITION, - = -net. 218 0d CENTRIFUGAL PUMPING MACHINERY. By E. W. SARGEANT, At Press. WATER SUPPLY: Selection of Sources and Distribution. By R. E. MIDDLETON, M.Inst.C.E., &c. With Plates and other Illustrations, -net. 88 6d SEA WATER DISTILLATION. By FRANK NORMANDY, - -net. 6s 0d THE TEPony OF THE STEAM TURBINE. By ALEX. Juve. Aone ee EDITIO. S GAS OIL, AND “AIR. ENGINES. Donxy, GRAVES “sMrrH, and BURSTALL, FIFTH EDITION, - ~ net. 25s 0d AERO ENGINES. By G. A. Burts, MInst.C.E. Tamp EDITION, : net. 88 6d Ad COMBUSTION ENGINES. By C. W. ASKLING and E. RORSLER, M.E net. 12s 6d DIESEL "ENGINES, LAND. AND MARINE. ‘By Prof. SUPINO. “Translated by G,. BREMNER and A. RICHARDSON, - - net. 128, 6d. EVOLUTION OF THE INTERNAL COMBUSTION ENGINE. By salir 4 ‘ BUTLER, - 8s 6 au GAS TURBINE ¢ onstruction and. Working ‘of Two Actual By H. HoLZWARTH and A. P. CHALKLEY, - net. 7s 6d achines). sucnnh GAS PLANTS. By Prof. C. A. SMITH. SECOND IMPREssion, niet, 5s 0d OIL_MOTORS: Their_Development, Construction, and Management. By G. LIECKFELD. In Handsome Cloth. Fully Illustrated, - - net. 15s 0d BOILERS, LAND AND MARINE. By T. W. TRAIL. FOURTH EDIrion, net. 10s 6d STEAM BOILERS: Their Defects, Management, and Construction. By R. D. Munro. Fourta EDITION, - - 48 6d OIL FUEL. By Epwarp BUTLER. THIRD EDITI0N, Revised, net. 7s 6d AUTOGENOUS WELDING. By GRANJON, RoOSEMBERG AND _ RICHARDSON. THIRD EDITION, - -net. 580d SMOKE ABATEMENT. By wn. NicHonson. With 59 Illustrations, -net. 68 0d LUBRICATION AND LUBRICANTS, By L. ARcHBUTT and R. M. DEELEY. THIRD EDITION, Thoroughly Revised, net. 25s 0d EMERY GRINDING MACHINERY. By R. B. Hopeson, A. M. Tnst.€. E. - net. 6s 0d THE POWER REQUIRED IN ROLLING MILLS. ByJ. Puppy, - - het. 12s 6d LOCOMOTIVE ENGINEERING. By W. F. PETTIGREW, M.Inst.C.E. THIRD EDITION, Revised throughout. New Illustrations, - - 21s 0d LOCOMOTIVE COMPOUNDING AND SUPERHEATING. By J F. GarRns, 8s 6d LIGHT RAILWAYS at Home and Abroad. By W. a. CoLE, M.Inst.C.E , - 163 0d MECHANICAL DRAWING. By J. E. JAGGER. M. Se. SEconp EDITION, - net. 7s 6d MECHANICAL ENGINEERING FOR BEGINNERS. By R. 8S. McLaReEn. Cloth. With 126 Illustrations. Srconp EDITION, - net. 58 0d sage TABLES: for the Calenlation of Wages on the Bonus ‘system: THE CALCULUS FOR “ENGINEERS AND PHYSICISTS. By Prof, ea av SMITH, A.M.Inst.C.E., &c. SECOND EDITION 73 6d MEASUREMENT CONVERSIONS (English aud French). 43 Graphic Tables or Diagrams on 28 Plates. By Prof. R. H. Smith, A.M.Inst.C.8 ,»&e., - 7s 6d MATHEMATICS AND MECHANICS. By C. A. A. CAPITO, M. on : -net. 12s 6d PRACTICAL SURVEYING AND FIELD- WORK. By V. G.’Sara PRACTICAL, CALCULATIONS FOR ENGINEERS. By C. B. ees ratates -E., &., and H. A. GoLDING, A.M.Inst.M.E. THrrp Ep ELEMENTARY GRAPHIC STATICS. By W. 7. Chawronne ovo ee aes CALCULATIONS ON THE ENTROPY- “TEMPERATURE CHAR, By W. a CRAWFORD, THE EFFECTS OF ERRORS IN SURVEYING. _By By. Bnreas, M. Se. on =e Crown 8vo. Cloth, net. 5s 8 Od eee lieth 5 LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND, GRIFFIN’S ENGINEERING PUBLICATIONS—Continued. VALVES AND VALVE GEARING. By CHARLES HURST. SEVENTH EDITION, With Important Appendix, - - - - : - - -net. 98 0d SCIENCE AND INDUSTRY: THEIR CO-OPERATION. By 8. R. Inzing. WoRTH, A.R.C.8c., &c. In Pocket Size, - : : : - - net, 1s 0d THERMO-DYNAMIC PRINCIPLES OF ENGINE DESIGN. By L. Hosss, net. 4s 6d ENGINEERING DRAWING AND DESIGN. By 8. H. WELLS, Wh.Se., &e. Vol. 1.—Practical Geometry, Plane, and Solid. SEVENTH EDITION, - ~- 4s 6d Vol. 11.—Machine and Engine Drawing and Design. FIFTH EDITION, 4s 6d HANDBOOK ON TOWN PLANNING. By J. JULIAN, - _ - -net. 5s 0d REFUSE DISPOSAL. by Prof. E. R. MaTrHEeWws. Fully Illustrated, -net. Gs 0d CIVIL ENGINEERING PRACTICE. By F, NoKL TAYLOR. 1,086 Illus., net 25s 0d THE MAIN DRAINAGE OF TOWNS. By F. Nok. TayLor. Fully Illus., net. 12s 6d MODERN DESTRUCTOR PRACTICE. By W. F. Goopricu. Fully Illus., net. 15s 0d ROAD MAKING AND MAINTENANCE. By THOMAS AITKEN SECOND ED., net. 21s 0d DUSTLESS ROADS: TAR-MACADAM. By J. WALKER SMITH, - - net. 10s 6d MODERN ROAD CONSTRUCTION, By FRANCIS Woob, M.Inst.C.E., -net. 4s 6d PETROL MOTORS AND MOTOR CARS. Comprising the Designing, Construc- tion, and Working of Petrol Motors. By F. STRICKLAND. SECOND EDITION, net. 18s 0d MOTOR CAR MECHANISM AND MANAGEMENT. By W. P. ADAMs. Part I.—The Petrol Car. THIRD EDITION, - - - - - -net. 58 0d Part II.—Electrical Cars, - = - - - 2 - - - -net. 58 0d CARBURETTORS, VAPORISERS, AND DISTRIBUTING VALVES, By Ep. BUTLER, -— - - - . - net. 68 0d THE AEROPLANE: A Concise Scientific Study. By A. FAGE, A.R.C.Sc. SECOND Eprrion, Beautifully Ilustrated, - - - : - net. 68 0d COMPENDIUM OF AVIATION. by Licut.-Col. HOERNES. Pocket Size, - net. 23 64 THE PROBLEM OF FLIGHT. By Prof. H. CHATLEY. SECOND EDITION, net. 10s 6d THE FORCE OF THE WIND. by Prof. HERBERT CHATLEY, B.Sc.,-net. 38 0d STRESSES IN MASONRY. By Prof. Hersert CHATLEY, B.Sc., -net. 3s 6d BUILDING IN EARTHQUAKE COUNTRIES. By A. MONTEL,- - -net. ss 6d CENTRAL ELECTRICAL STATIONS (Design, Organisation, and Management). By C. H. WorpinaHaM, A.K.C. SEcoND EDITION, net. 24s 0d ELECTRICITY METERS. By Il. G. SoLomon, -_ 5 5 + + = net. 168 Od TRANSFORMERS, By Prof. H. BonLe and Prof. D. ROBERTSON,- —- ~—- net. 218 Od ELECTRIC CRANE CONSTRUCTION. Ly C. W. HILL, A.M.I.C.E., - net. 258 0d ELECTRICAL PHOTOMETRY. By Prof. 0. BoHLE, M.I.E.E. Fully Illus., net. 10s 6d ELECTRO-METALLURGY. By WALTER G. McMILLAN, F.1.C., F.C.8. THIRD EpITION, Revised and Enlarged by W. R. CooPER. Demy 8vo., a -net. 128 6d ELECTRICAL PRACTICE IN COLLIERIES. By Prof. > Burns, M.E. Cloth. Fourrim Eprrion, Revised. With numerous I]lustrations.. — . net, 7s 6d ELECTRICITY IN MINING. By SIEMENS BrRos., Ltd.,- — - - net, 108 6d WIRELESS TELEGRAPHY. By Gustav E1ounorn, Ph.D., - - -net, ss 6d TELEGRAPHIC SYSTEMS, and Other Notes. By ARTHURCROTCH, net. As 0d ELECTRICAL RULES AND TABLES (A Pocket-book of). By JouN MUNRO and Professor JAMIESON. NINETEENTH EDITION, Revised. Pocket size. Leather, $s 6d ELECTRICAL THEORY AND THE PROBLEM OF THE UNIVERSE. By G. W. de TUNZELMANN, - : : : - : - -net. 15s 0d THE THEORY OF STATICS. By G. Upny YULE. Skconp EpiTIoN, —- net. 10s 6d WORKS BY W. J. MACQUORN RAMKINE, LL.D., &c. CIVIL ENGINEERING (A Manual of). TWENTY-FouRTH EDITION, 168 Od A MANUAL OF APPLIED MECHANICS. NINTEENTH EDITION, - + - 128 6d A MANUAL OF MACHINERY AND MILLWORK. SEVENTH EDITION, - 128 6d A MANUAL OF THE STEAM ENGINE AND OTHER PRIME MOVERS. SEVENTEENTH EDPITION,- - - = - - + © = = ~ 128 6d A MECHANICAL TEXT-BOOK: A pea Introduction to the Study of Mechanics. By Prof. RANKINE and C. E. BAMBER. FIFTH EDITION, 9s Od USEFUL RULES AND TABLES: For Architects, Builders, Engineers, Founders, Mechanics, Shipbuilders, Surveyors, &c, EIGHTH EDITION, 10s 6d WORKS BY PROF. A. JAMIESON, M.Inst.C.E. STEAM AND STEAM ENGINES (Advanced). SEVENTEENTH EDITION, - 108 6d APPLIED MECHANICS AND MECHANICAL ENGINEERING. Vol. I.— Applted Mechanics, 6s. Vol. II.—Strength of Materials, 5s. Vol. III.— Theory of Structures, 5s. Vol. IV.—Hydraulics, 5s. Vol. V.—Theory of Machines, 7s 6d. ° HEAT ENGINES: STEAM, GAS, AND OIL (Elementary Manual of). Four- TRENTH EpITIon, Revised and Enlarged by E.S. Andrews, - - -net. 88 0d MAGNETISM AND ELECTRICITY (Practical Elementary Manual of). NINTH EpItion, Revised and Enlarged, : a = - : - - 88 6d APPLIED MECHANICS (Elementary Manual of). TENTH EDITION. Revised and Greatly Enlarged. - : - - < < « . i - 38 6d LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S BOOKS ON MARINE ENGINEERING AND NAVAL ARCHITECTURE. A MANUAL OF MARINE ENGINEERING. By A. E. SEATON, M.Inst.C.E., M.I.Mech.E., M.Inst.N.A. SEVENTEENTH ED., Revised. net. Tue as OF THE STEAM TURBINE. By ALEXANDER JUDE. sacen? GRIFFIN'S ‘NEW GUIDE TO THE B.0.T. EXAMINATIONS FOR ‘MARINE ENGINEERS. Vol. I.—Calculations for Marine Engineers,. . . net. Vol. II.—Elementaries, Verbals, and Drawing, a . net. DIESEL ENGINES, By SUPINO, BREMNER, and RICHARDSON, . | _. net. a PRINCIPLES OF ENGINE DESIGN. By L. ae : . net. ENGINE- ROOM PRACTICE. * By “Joun G. LIVERSIDGE, RN. | EIGHTH EpITIoN, Revised and Enlarged, . . net. SEA WATER DISTILLATION. By FRANK NORMANDY. In Handsome Cloth. Fully Illustrated, . - net. MARINE ENGINEERING RULES AND TABLES. ‘By A. E, SEATON and vie ROUNTHWAITE. TWELFTH EDITION, Thoroughly Revised. Pocket c - net. THE “SCREW PROPELLER, ‘and Other’ Competing Instruments of Marine Propulsion. By A. E. SEATON, M.Inst.C.E. Fully Illustrated. net. THE DESIGN AND CONSTRUCTION OF SHIPS. By Sir J. H. BILEs, LL.D., &c. Vol. I.—Calculations and Strength. With 36 Folding Plates and 9245 other Illustrations. Complete in itself, with Index, = ae II.—Stability, Resistance, Propulsion, and Oscillations. Complete “with n STEEL ‘SHIPS. Their Construction and Strength. “By THoMas “Watton. FourtH EDITION, Greatly Enlarged, . . net. PRESENT DAY SHIPBUILDING. SPO Shipyard Students, “Engineers, &e. By THomMAS WALTON. Fully Illustrated, . net. THE SAE: OF SHIPS. By Sir ‘Epwarp J. REED, EK.C.B,, FERS., “MP. In Large 8 . HYDROGRAPHIC SURVEYING. For the Use of Beginners, Amateurs, and Port and Harbour Masters. ad Commander 8. Saale of the R.N. College, Greenwich, : . é : : . net. GRIFFIN’S NAUTICAL SERIES. Elementary Seamanship. By D. WILSON-BARKER. SIXTH EDITION, . i Know Your Own Ship. yT, Watton & J. KInG. THIRTEENTH HDIBION, net. Trigonometry. By R. C. Buck. THIRD EDITION, z Practical Algebra. By R. C. RUCK. SECOND EDITION, 5 5 Practical Mechanics. By T. MACKENZIE THIRD EDITION, Navigation: Theoretical and Practical. By D. - WILsoN- BARKER and W. ALLINGHAM. THIRD EDITION, . Marine Meteorology. By W. ALLINGHAM,. . 8 Latitude and Longitude. By W. J. MILLAR. SEC: OND EDITION, The Legal Duties of Shipmasters. By B. W. Ginszure. THIRD EDITION, A Medieal and Surgical Help for Shipmasters. By W. JOHNSON SMITH. FouRTH’ EDITION, Revised by ARNOLD CHAPLIN of the P. & 0. Coy., _. net. English-Spanish & Spanish-English Sea Terms & Phrases. By Fleet- Paymaster GRAHAM-HEWLETT. Pocket Size, . . net. Definitions in Navigation & Nautical Astronomy. ‘By! Groves-SHOW ELL, L.C.C. School, Poplar. Illustrated, . . net. ee Duties of Shipmasters, — By “Capt. W. HARRY WILKES. 01 net. Nature Notes for Ocean Voyagers. By Captains CARPENTER and Wrison: BARKER, . ee ee . < : : . net. PHYSICS. A Tat BOOK OF PHYSICS. By Prof. J. H. Poyntine and Sir J. J. THOMBON: I.—Properties of Matter. S1xTH EDITION, fi Vol II.—Sound. SrxtH EpiTion, . ‘ : : a ‘ * . Vol. III.—Heat. FourtH EDITION, F ‘ . . . Vol. IV.—Parts I. and II. Electricity and Magnetism, i ‘ ELEMENTARY TEXT-BOOK OF RALTEIGS: By Dr. R, WALLACE STEWART. Vol. I.—General Physics, . ‘ E 3 . net. Vol. II,—Sound, . 3 c ri P a ‘ ‘i . a . net. Vol. IlI.—Light,. . c r , : : Ff ei i 3 . net. Vol. IV.—Heat, ni 5 . é - net. 28s Od » 188 Od 8s 6d 8s 6d 128 6d 4s 6d 6s Od 6s 0d 8s 6d 12s 6d net. 25s 0d net. 25s 0d 18s 0d 7s 6d 25s 0d 12s Od 4s 6d 28 6d 38 6d 38 6d LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S MINING AND GEOLOGICAL WORKS. ORE AND STONE MINING. By Sir C. LE NEVE Foster, DSe., F.R.S8. SIXTH EDITION, Revised by Prof. §. H. Cox, A.R.S. M., - net. 28s 0d THE ELEMENTS OF MINING AND QUARRYING. By Sir C. LE NEVE Foster, D.Sc. Revised by Prof. $8. H. Cox. SECOND EDITION, - -net. 7s 6d METHODS OF AIR ANALYSIS. By J. 8. HALDANE, MD. LL.D. ih Crown 8vo., -net. 5s 0d THE. co OF MINES. By Prot. J. CaDMAN and J. S. iase M.D., ‘At Press. A eee BOOK OF COAL- MINING. By H. W. HUGHES, F.G.S. FIFTH EDITION, Revised and Enlarged. With 4 Plates and 670 Illustrations, net. 24s 0d PRACTICAL COAL-MINING. By Guorar L. ERRR, MLE. FIFTH EDITION, Rewritten and Greatly Enlarged, - -net. 12s 6d ELEMENTARY COAL-MINING. By GEORGE 4 KERR, M.E. With 200 Illustrations. THIRD EDITION, Revised, - - 88 6d MINE SURVEYING. By Bannert H. BRrovaH, F. 6. 8. FOURTEENTH EDITION by H. DEAN, M.Sc., A.R.S.M , - - At Press. TREODOBITE SURVEYING AND LEVELLING. By Prof. JAMES PARK, F.G In Crown 8vo. Cloth. Ilustratea. THIRD Epitron, - -net. 10s 6d THE EFFECTS OF ERRORS IN SURVEYING. By Hy. Briggs. With Frontispiece and 22 Illustrations, - : -net. 5s Od PRACTICAL SURVEYING AND FIELD-WORK. By V.G. SALMON, At Press. MINING GEOLOGY. A ‘ext-Book for Mining Studentsa and Miners. By JAMES PaRK, F. G. S., M.Inst.M.M. THrrp EDITION, - = net. 63 Od PROSPECTING FOR MINERALS. By Prof. S. HERBERT Cox. SIXTH EpItion, Revised, - 53 Od men LAW OF THE BRITISH EMPIRE, By CHARLES. J. ALFORD, F. G.s. ‘ e - net, 8s 6 iegneen MINE VALUATION. By M. A. Bunsiasy, B. Se. Fpst i-xi it 160. Fully Illustrated, - net. 108 td MINE ACCOUNTS AND MINING BOOK - KEEPING. By J. G. Laws, Assoc.R.S.M, FIFTH IMPRESSION, - - 10s 6d THE MINING ENGINEER’S REPORT BOOK AND DIRECTORS’ AND SHAREHOLDERS’ GUIDE. By EDWIN R. FIELD. THIRD EDITION. Pocket Size. Leather, - 33 6d ELECTRICITY IN MINING. By SIEMENS Bros., Ltd. Vv ery besntnuny Illus. trated. Printed on Art Paper, - - -net. 108 6d ELECTRICAL PRACTICE IN COLLIERIES. By Prof. D. Burns, M.E., M.Inst.M.E. Fourtu EpDItTIon, Revised and Enlarged, net, 78 6d PRACTICAL HYDRAULICS FOR MINING STUDENTS. by Prof. a EAGE, al! Press, BRIQUETTING. By G. FRANKE, Trans. by F. LANTSBERRY, alf Press, ga ee ch diab IN DIFFICULT CASES. By J. RIEMER and J: a - net. 10s BLASTING ; And the Use of Explosives. By 0. GUTPMANN. SECOND EDITION 10s 6d TESTING ‘EXPLOSIVES. ‘By Cc. E. BICHEL and AXEL LARSEN. Ww ith oe lates, 6s Od SPANISH- ENGLISH AND ENGLISH- SPANISH MINING, METALLURGICAL, AND ALLIED TERMS. By EDWARD HALSE, A.R.S.M. Cloth. SECOND EDITION, - - net. 10s 6d GETTING GOLD. A Gold. amining Handbook ‘for Practical Men. By De Ck BS, JOHNSON, F.G.S., A.I.M.E. THIRD EDITION, - E m - 38 6d GOLD-SEEKING IN SOUTH AFRICA. A Handbook of “Hints. By THEO. Kassner. Illustrated, - < 4s 6d A TEXT-BOOK OF GEOLOGY. By Prof. JAMES PARK. Very fully se: i" trated, t. 15s 0 STRATIGRAPHICAL GEOLOGY AND PALEONTOLOGY (on the Basis Phillips). By R. ETHERIDGE, F.R.S - 343 Od A TEXTBOOK OF GEOLOGY. by Prof. JAMES PARK, F.G8 -Profusely a Illustrated, ds THE EARTH: ITS GENESIS AND “EVOLUTION. By A. “T, SWAINE. With 11 Plates and 53 other Illustrations, - - net. 7s 6d AIDS IN PRACTICAL GEOLOGY. By Prof. G. COLE, MRLA. SIXTH aaa - 10s DITION, - + - + = + < GEOLOGY ale ENGINEERS. By Lieut,-Col. RB. ¥, SORSBIE. Fully Illustrate - net. 10s 6d MINERAL WEALTH AND GEOLOGY OF CHINA. ByC.Y.Wanc, - net. 38 0d LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S METALLURGICAL SERIES. AN JiTRODUerION TO METALLURGY. By Sir W. C. RoBERTS- AUSTEN, .S.M, SIXTH EDITION, by F, W. HARBORD, A.R.S.M. net. 18s 0d THE METALLURGY OF GOLD. By Sir T. Kirke Kose, D. 8c, Chemist and Assayer to the Royal Mint. SrxrH EDITION, Revised and re-written, - net. 22s 6d THE METALLURGY OF SILVER. By aor. CoLLins, Assoc. R.S.M., M.Inst.M.M. SECOND EDITION, - In Preparation. THE METALLURGY OF LEAD. An Exhaustive Treatise on the Manufac- ture of Lead. By A. F. COLLINS, Assoc.R.S.M., M.Inst.M.M, SECOND EDITION, Revised, - - -net. 21s 0d THE METALLURGY OF THE NON- FERROUS METALS. ‘By wnt. GOWLAND, F.R.S., Prof. of Metallurgy, Royal School of Mines, - - -net. 18s 0d THE METALLURGY OF STEEL. By Ll. W. HARBORD, Assoc.R. §.M., F.LC., and J. W. HALL, A.M.Inst.C.k. Pier EDITION. In two volumes. THE METALLURGY OF IRON. By THomasS TURNER, Assoc.R.S.M., F.LC., Prof. of Met., Birmingham Univ. FourtH EDITION, Revised and Enlarged. ba ge AND THEIR INDUSTRIAL APPLICATIONS. by EpWarp F, Law, $.M. SECOND EDITION, Revised, - net, 12s 6d SAMPLING AND ASSAY OF THE PRECIOUS METALS. By E. A, SMITH, .R.S.M., : net. 15s 0d ANTIMONY : Its History, Chemistry, Mineralogy, Geology, Metallurgy, Preparation, &e. Y. WANG. In Large 8vo. Cloth. Illustrated, net. 12s 6d ROBERTS-AUSTEN ; yeaneeee and Scientific Papers. By S. W. SMITH, - net. 21s 0d THE METALLURGY OF COPPER. ByT.C. CLoup, A.R.S.M. In Preparation. OTHER METALLURGICAL WORKS. RAND TA EUR SIGSG PRACTICE. In Two Volumes. Vol. I.—SECOND EDITION, net. 21s. Vol. II., - - - -net. 21s 0d MODERN COPPER SMELTING, LECTURES ON. By D. M. LEvy, - net. 10s 6d CAST IRON IN THE LIGHT OF RECENT RESEARCH. By W. H. HATFIELD, .Met. Profusely Illustrated, - = net. 10s 6d CYANIDING GOLD AND-SILVER ORES. By H. FORBES JULIAN and Ep¢saRr SMART, A.M.Inst.C.E. SECOND EDITION, - net. 21s 0d THE CYANIDE PROCESS OF GOLD EXTRACTION. By Prof. JAMES per ¥.G.S. Firta ENGLISH EDITION, - net. 8s 6d TEXT-BOOK OF ASSAYING. By J. J. BERINGER, FIC, FOS, and C. BERINGER, F.C.S. THIRTEENTH EDITION. Illustrated, - - 10s 6d PRACTICAL ASSAYING. By Prof. Jas. PARK, - -net. 7s 6d MERA LLURGICAE ANALYSIS AND ASSAYING. A Three Years’ Course. By W. A. MACLEOD, B.A., B.Sc., and CHAS. WALKER, F.C.S., - - -net. 12s 6d MINERALOGY OF THE RARER METALS. By B. CAEN and W. sae a TTO. 6s micRoscoric ANALYSIS ‘OF METALS. By FLoris Osmonp aud J. EB stean, R.S. SECOND EDITION. By L. P. SIDNEY, - - -net. 8s 6d METALLIC ALLOYS: Their Structure and Constitution. By G. H. GULLIVER, B.So., F. R.S.E. SECOND EDITION, Thoroughly Revised, -net. 10s 6d INTRODUCTION TO PRACTICAL METALLURGY. By Prof. T. TURNER, net. 3s 0d ELEMENTARY METALLURGY. By A. H. SEXTON, F.1.C. Fourtu Epn. 5 6s 0d LECTURES ON IRONFOUNDING. By Prof. T. TURNER. SECOND E Eprrion, net. 8s 6d GENERAL FOUNDRY PRACTICE. By A. McWrILut1AM, A.R.S.M., and PERCY LoNemum. In Medium 8vo. SECOND EDITION, Revised, - a -net. 16s 0d NOTES ON FOUNDRY. PRACTICE. By J.J. Moran, F.C. S., “net. 2s 6d BLAST FURNACE PRACTICE. By J. un Mor@an, FOS. -net. 1s 6d SMITHY AND NORGE, Scie nee in. By H. CATHCART, - -net. 4s 0d ELECTRIC SMELTING AND REFINING. ‘By Dr. W. BoRCHERS and W. G. MCMILLAN. SECOND EDITION, — - -net. 21s 0d TREATISE ON ELECTRO- METALLURGY. By W. G. McMILLAN and W.R CooPER. THIRD EDITION, Revised, - = = ae 12s 6d WORKS ON PETROLEUM. PETROLEUM AND ITS PRODUCTS. By Sir BovERTON REDWoOD, D.Sc. THIRD EDITION, Revised, - - net. 50s 0d A HANDBOOK ON PETROLEUM, for Inspectors under the Petroleum Acts. By Capt. J. A. THOMSON, Sir. B. REDWvOD, and Major CooPpER-KEY. THIRD EDITION, Revised, -net. 8s 6d THE PETROLEUM TECHNOLOGIST’S POCKET- BOOK. By Sir BOVERTON REDWOOD and ARTHUR EASTLAK -net. 8s 6d THE STORAGE OF PETROLEUM ‘SPIRIT, By Major A. Coorsr- Kny. -net. 28 6d OIL FUEL. Its Supply, Composition, and Application. By Epwarp BurLER. M.I.Mech.E. THIRD EDITION, Revised and Enlarged, - -net. 7s 6d LABORATORY HANDBOOK OF MINERAL OIL TESTING: By J. A. Hicks. SECOND EDITION, Revised, -- - -net. 2s 6d LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S TECHNICAL PUBLICATIONS. ener ery for Engineers and Manufacturers. By BERTRAM BLOUNT, C., and A. G. BLoxaM, F.LC. Vol. LS: : 4 fs Vol. II. SEconD EDITION, : bce ae a Oils, Fats, Butters, and Waxes, By C, R, ALDER WRIGHT, D.Sc. Revised by C. A. MITCHELL, B.A., F.1.C. SECOND EDITION. With 800 pages, -net. 25s 0d Oils, Resins, and Paints: Analysis and Valuation. By H. INGLE, D.Sc., net. 3s 6d Physico-Chemical Tables. By J. CASTELL-EVANS, F.I.C. Vol. I.—Chemical Engineering, - : - net. 248 0d Vol. IL. —Physical and. Analytical Chemistry, - net. 36s 0d GHaTtILAtV es Inorganic Analysis. By Dr. J. W. MELLOR. Very fully ime trated throughout,- —- net. 303s 0d Water grees? for Sanitary and Technical Purposes. By H.B. srooxs, -net. 4s Gd Methods ae Air Analysis. By J. 's. HALDANE, M. D. EE: D., BRS. Fully lustrate - net. 5s 0d Foods: Their ‘Composition and Analysis. By A. W. and M. W. BLYTH. SIXTH EDITION, - - 21s Od Poisons: Their Effects and Detection. By A. and M. BLYTH. FouRTH EDITION, - - net. 21s 0d Flesh Foods: Chemical, Microscopical and Bacteriological Examina- tion. By C. A. MITCHEL LL, - 10s 6d Dairy Chemistry. By dH. DROOP Ricumonp, FI. C. , Analyst to the ‘Aylesbury Dairy Co. SECOND EDITION, - e -net. 15s Od Dairy Analysis. By H. Droop RICHMOND, FI. C. SECOND EDITION, Thoroughly Revised. Crown 8yo. Illustrated, ° - - -net. 2s 6d Milk: Its Production and Uses. By EDWARD F. WILLovaHy, M.D. - net. 68 0d Elementary Agricultural Chemistry. By HERBERE INGLE, BSc. SECOND EDITION, - -net. 4s 6d Agricultural Bacteriology. By Lonis, STEV ENSON, and “gurrH, -net. 48 td The Principles and Practice of Brewing. By Dr. W. J. 8YKES. THIRD EpITION, Revised by A. R. LIne, F.1.C., — - > net, vis Od Technical "Mycology. Dr. F. Laran. SECOND Epirion. it Two Vols. Vol. I., net. 15s Od; Vol. II., net. 24s 0d Micro-Organisms and Fermentation. By ALFRED JORGENSEN. FOURTH EpITI10Nn, Completely Revised. Translated by S. H. DAVIES, B.Sc , - net. 15s 0d Ferments and Their Actions. ByC. OPPENHEIMER, Translated by C, A. MITCHELL, B.A., F.I.C. In Cloth, - -n 7s 6d Meets Its Manufacture and Examination. By Cc. A MITCHELL, B. A, Rone -fhet. 838 Gd Peat: Its Use and Manufacture. By P. BJORLING and F. GIssiNe. net, 6s 0d Commercial Peat: Its Uses and Its Possibilities. By F, T, Gissixo. In Crown 8vo. Cloth, - - -net. 68 0d Paneer Technology. By R. w. SINDALL, F. C. 8. In Medium 8vo. Handsome Cloth, Illustrated. SECOND EDITION, Revised, - -net, 12s 6d Stationery Testing. By H. A. BROMLEY. Fully Illustrated, - -net. 2s 6d The Clayworkers’ Handbook. By A. B. SEARLE. SECOND EDITION, Revised. In Cloth, - -tiet. 68 Od British Clays. Shales, and Sands. By A. B. SEARLE. Mlustrated, -net. 78 6d Refractory Materials. By A. B. SEARLE, At Press. Ceramic Literature. Compiled, Classified, and Described by M. L. Sonow, net, 42s 0d Art of the Goldsmith and Jeweller. By T. B. WIGLEY. SECOND EDITION, Revised, and with 12 New Plates, - - -net. 73 6d Modern Methods of Sewage Purification. By G. BERTRAM KERSHAW. Fully Illustrated, - - - net. 21s 0d The Principles of Sewage Treatment. By Prof. DUNBAR of Hamburg. Translated by H. L. CALVERT, M.Sce., - : -net, 15s 0d Trade Waste Waters. By H. WILSON, M. D., and ‘EL T. CALVERT, Ph.D. With 22 Plates and many other Illustrations, = - - - net. 18s 0d Trades’ Waste: Its Treatment and Utilisation. By Ww. Naytor, F.C.S., &e. Illustrated, - ~ net. 21s 0d Refuse Disposal. By Prof. E. R. MATTHEWS, : -net. 68 0d Smoke Abatement. By Wm. NICHOLSON. With Illustrations, -net. 6s 0d Town Planning. By JuLIAN JULIAN, B.E., - _-net 5s 0d Caleareous Cements. ByG. R. ‘REDGRAVE and ‘CHARLES. SPACKMAN, F.c.8 SECOND EDITION, - - ' = net. 15s 0d Handbook for Cement Works’ Chemists. “By FRANK B, ‘GATEHOUSE, F.C.S, In Handsome Cloth, -net. 5s 0d Gas ip eouinckure: By w. J. rs BUTTERFIELD. Vol. I, -net, 7s 6d 5 ea. na - Shortly. eta tatorine Power of Coal Gas. By J. CosTE, : epet. G8 Fuel: Gaseous, Liquid and Solid. hy J. H. CosTE and FE. R. ANDREWS. net. 6s 0d Acetylene. By F. H. LEEDS and W. J. A. BUTTERFIELD. SECOND EDITION, net. 8s 6d Fire and Explosion Risks. By Dr. Von Schwartz. InCloth, - - net. 16s 0d Practical Sanitation. By Gro. REID, M.D. With Appendix on Sanitary pe Ss Law, SEVENTEENTH EDITION, - - = LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S TECHNICAL PUBLICATIONS. Lessons on Sanitation, By J. W. Harrison, M.R.San.I., -net. 38 6d Sanitary Engineering. By FRANCIS Woop, Ae M. Inst. C. E. THIRD EDITION, - -net. 8s 6d Modern Destructor Practice. By Ww. ¥. GoovrIcH. Illustrated, - -net. 15s 0d Road Making and Maintenance. By THOS. AITKEN, A M.Inst.C.E. SECOND EDITION, - oe - -net, 21s 0d Dustless Roads: Tar- Macadam. By J. W. SMITH, -net. 108 6d Modern Road Construction. By Francis Woop, -net. 48 6d Handbook on Town Planning. By J. JULIAN, -net. 5s 0d Enamelling on Iron and Steel. By JULIUS GRUNWALD. Cloth. Illustrated. net. 6s 0d Technology of Iron Enamelling and Tinning. By JULIUS GRUNWALD, net. 6s 0d Raw Materials of the Enamel Industry. By J. GRUNWALD, -net. 8s 6d Treatise on Colour Manufacture. By GEORGE ZERR and Dr. RUBENCAMP. English Edition by Dr. C. MAYER, of Burgdorf. Pbrofusely Illustrated, - net. 30s 0d Tests for Coal-Tar Colours in Aniline Lakes. By GEORGE ZERR. Trans- lated by Dr. C. MAYER, -_ - - -net. 10s 6d Painting and Decorating. A Complete Practical Manual. By W. J. PEARCE. Fourta EDITION, Revised and Enlarged, - 128 6d Painters’ Colours, Oils, and Varnishes. G. H. ‘Horst, F. Cc. s. Fura EDITION, Revised and Enlarged. By NOEL HEATON, B.Sc., - net. 10s 6d Painters’ Laboratory Guide. By G. H. Hurst, F.C.S. In Cloth, - 58 0d The Chemistry of the Colloids. ‘By Dr. V. PéscHL. Translated by Dr. H. Hopason, - - - -net. 33 6d Celluloid: Its Manufacture, “application, and Substitutes. From the French of MASSELON, ROBERTS, AND CILLARD. By Dr. H. H. Hopeson, - net. 25s 0d Chemistry of India Rubber. By Cc. 0. MVEBER: Ph.D. THIRD IMPRESSION. With many Illustrations, : - -net. 16s 0d The Manufacture of Rubber Goods. By ADOLF HEIL and ‘Dr. W. Esou. Translated by E. W. LEWIS, A.C.G.I. In Cloth. Illustrated, - : - net. 10s 6d Glue, Gelatine, and Their “Allied Products. By THoMAS LAMBERT. In Large Crown "evo. Fully Illustrated, - -net. 5s 0d Leather Trades Chemistry. By 5S. R. TROTMAN, M. A, F. L Cc. In Handsome Cloth. Fully Illustrated, - - net. 15s 0d Ink Manufacture. By C. A. MITCHELL, BA, FLC., and T. C. HEPWORTH. SECOND EDITION, Revised. Re-set on ‘Larger Page. In Cloth. With Plates and Illustrations. A Manual of Dyeing. By E. Knecut, Ph.D., Cor. Rawson, F.1.C., and R. LoEWENTHAL, Ph.D. THIRD EDITION, Thoroughly Revised and Re- written, - 458 0d Synthetie ‘Dyestuffs, and, the ‘Intermediate Products from which they are Derived. By J. C. CAtn, D.Sc., and J. F. THORPE, Ph.D. SECOND EDITION, Revised, - - net. 16s 0d The Analysis of Dyestuffs. ‘By ARTHUR E. GREEN, M. Se, BR. 8, F.LC. Illustrated. SECOND EDITION, - - -net. 8s 6d Digitonary 2 of Dyes, Mordants, and Other Compounds. By Cr. Rawson, E.LC., M. GARDNER, F.C.S., and W. F. Laycock, Ph.D. In Large 8vo. Cloth, ‘rerary Style, - - net, 16s 0d Spinning aud Twisting of Long Vegetable Fibres (Flax, Hemp, pba Tow, and Ramie). By H. R. Carter, -net. 16s 0d The Cotton Weavers’ Handbook. By H. B. HEYLIN. In Cloth, - -net. 6s 0d Buyers and Sellers in the Cotton Trade. By H. B. HEYLIN. With Chronological and Statistical Chart, - -net. 8s 6d Textile Fibres of Commerce (Oceurrence, Distribution, Preparation, and Uses). By W. I. HANNAN. In Cloth. With Illustrations, - -net. 9s 0d BIbaEUERE, and_ Finishing of Cotton. By &. R. TROTMAN, M.A., and E. L. THorP, M-I.Mech.E., -net. 16s 0d Textile Printing. By E. KNECHT, Ph.D., and J. B. ‘ForHERGIL. With 13 Plates and 86 Patterns in the Text, - - net. 36s 0d Textile Printing. By C. F. 8. ROTHWELL, FOS. With Tilustrations, - - 21s Od Engraving for Calico-Printing. By WM. BLAcKWoopD, - net. 10s 6d Dyeing and Cleaning. By FRANK J. FARRELL, M.Sc. In Cloth. With 76 Illustrations. THIRD EDITION, Enlarged, - : -net. 6s 0d Bleaching and Calico Printing. By G. DUERR & WM. TURNBULL. - - 12s 6d Text-Book of Inorganic Chemistry. Edited by J. Newron FRIEND, D.Sc. In IX Vols. (See General Catalogue.) Elementary Practical Chemistry. By J. E. MyrRs and J. B. FIRTH, - net. 4s 0d Inorganie Chemistry, By A. DUPRiand WILSON HAKE. THIRD EDITION, net. 6s 0d Elements of Chemical Engineering. By J. GROSSMANN, Ph.D. 2ND ED., net. 388 6d Outlines of Quantitative Analysis, By A. H. SExton, F.I.C. FirtH EDITION, 3s 0d Outlines of Qualitative Analysis. By A. H. Sexton, F.1.C. FourTH EDITION, 3s 6d LONDON: CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. GRIFFIN’S TECHNICAL PUBLICATIONS. Lessons on Sanitation, By J. W. Harrison, M.R.San.I., -net. 388 6d Sanitary Engineering. By FRANCIS Woop, A. M. Inst. C. E. THIRD EDITION, -net. 8s 6d Modern Destructor Practice. By w. ¥. GoovrRIcH. Illustrated, - -net. 15s 0d Road Making and Maintenance. By THOS. AITKEN, A.M.Inst.C.E. SECOND EDITION, - : - . - net, 21s 0d Dustless Roads: Tar- Macadam. By J. W. SMITH, -net. 108 6d Modern Road Construction. By FRaNcIs Woop, -net. 4s 6d Handbook on Town Planning. By J. JULIAN, -net. 5s 0d Enamelling on lron and Steel. By JULIUS GRUNWALD. Cloth. Illustrated. net. 6s 0d Technology of Iron Enamelling and Tinning. By JULIUS GRUNWALD, net. 6s Od Raw Materials of the Enamel Industry. By J. GRUNWALD, -net, 8s 6d Treatise on Colour Manufacture. By GEORGE ZERR and Dr. RUBENCAMP. English Edition by Dr. C. MaYER, of Burgdorf. Profusely Illustrated, - net. 30s 0d Tests for Coal- var fom in Aniline Lakes. By GEORGE ZERR. Trans- lated by Dr. C. MAYER, - - -net. 10s 6d Painting and Decorating. A “Complete Practical Manual. By Ww. J. PEARCE. FourTH EDITION, Revised and Enlarged, - 128 6d Painters’ Colours, Oils, and Varnishes. G. H. Hurst, F. Cc. 8. Fura EDITION, Revised and Enlarged. By NoEL HEATON, B.Sc., - net. 10s 6d Painters’ Laboratory Guide. By G. H. Hurst, F.C.S. In Cloth, - - 53 0d The Chemistry of the Colloids. By Dr. V. PosoHL. Translated by Dr. H. Hopaeson, - - -net. 33 6d Celluloid: Its Manufacture, “Application, and Substitutes. From the French of MASSELON, ROBERTS, AND CILLARD. By Dr. H. H. Hopeson, - net. 25s 0d Chemistry of India Rubber. By C. 0. WEBER, Ph.D. aaiD IMPRESSION. With many Illustrations, - : - net. 16s 0d The Manufacture of Rubber Goods. By ADOLF HEIL and ‘Dr. W. Escu. Translated by E. W. LEWIS, A.C.G.I. In Cloth. Illustrated, - - net. 10s 6d Glue, Gelatine, and Their “Allied Products. By THOMAS LAMBERT. In Large Crown 8vo. Fully Illustrated, - - -net. 5s 0d Leather Trades Chemistry. ByS. R . TROTMAN, M. A, F. L C. In Handsome Cloth. Fully Illustrated, - : -net. 15s 0d Ink Manufacture. By C. "A. MITCHELL, BA, FLC., ‘and T. C. HEPWORTH. SECOND EDITION, Revised. Re-set on ‘Larger Page. In Cloth. With Plates and Illustrations. A Manual of Dyeing. By E. KnEcuT, Ph.D., CHR. Rawson, F.I.C., and R. LOEWENTHAL, Ph.D. THIRD Eprtiow, Thoroughly Revised and Re- written, - 45s 0d Synthetic Dyestuffs, and ‘the ‘Intermediate Products from which they are Derived. By J. C. Carn, D.Sc., and J. F. THORPE, Ph.D. SECOND EDITION, Revised, - net. 16s 0d The Analysis of Dyestuffs. ‘By ARTHUR E. GREEN, M. Se. Er R. 8. Fr. LC. Illustrated. SECOND EDITION, - -net. 8s 6d Dictionary of Dyes, Mordants, and Other Compounds. By Cm. ” RAWSON, F.LC., W. M. GARDNER, F.C.S., and W. F. Laycock, Ph.D. In Large 8vo. Cloth, Library Style, - - net, 16s 0d Spinning and Twisting of Long Vegetable Fibres (Flax, Hemp, pt Tow, and Ramie). By H. R. Carter, - net. 16s 0d The Cotton Weavers’ Handbook. By H. ’B, HEYLIN. In Cloth, - -net. 68 0d Buyers and Sellers in the Cotton Trade. By H. B. HEYLIN. With Chronological and Statistical Chart, - - -net. 8s 6d Textile Fibres of Commerce (Occurrence, Distribution, Preparation, and Uses). By W. I. HANNAN. InCloth. With Illustrations, - -net. 9s 0d Bleaching and Finishing of Cotton. By S. R. TRoTMAN, M.A., and EB. L. THorp, M-I.Mech.E., - net. 16s 0d Textile Printing. By E. KNECHT, Ph.D., and J. B. ‘ForHERGILL. With 13 Plates and 86 Patterns in the Text, - -net. 36s 0d Textile Printing. By C. F. S. ROTHWELL, FC. s. With Tuustrations, : - 21s 0d Engraving for Calico-Printing. By WM. BLackwoop, - net. 10s 6d Dyeing and Cleaning. By FRANK J. FARRELL, M.Sc. In Cloth. With 76 Illustrations. THIRD EDITION, Enlarged, : -net. 58 0d Bleaching and Calico Printing. By G. DuzERR & WM. TURNBULL. - . - 12s 6d TER Book of Inorganic Chemistry. Edited by J. NEWTON FRIEND, D.Sc. In IX Vols. (See General Catalogue.) Elementary Practical Chemistry. By J. E. MyERS and J. B. FrrtH, - net. 4s 0d Inorganic Chemistry, By A. DUPRiand WILSON HAKE. THIRD EDITION, net. 68 0d Elements of Chemical Engineering. By J. GRossMANN, Ph.D. 2ND ED., net. 38 6d Outlines of Quantitative Analysis, By A. H. SExTon, F.I.C. FirtH EDITION, 3s 0d Outlines of Qualitative Analysis. By A. H. Sexton, F.I.C. FouRTH EDITION, 3s 6d LONDON: CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. * Wat 94 aA: ; were NS eels i PR MA inate : > STARA sii wearer: ‘ wy yah Was My. hoe Meee se G SPELT LE FUER AU Oa aaa,